update: Upgrade Section & Extensions

This is a partial rewrite of 6365. This moves the Upgrade section to the
`UPGRADING.txt` file and updates the verbiage to link to the Upgrade
Guide in the docs as well as the `UPGRADING.txt` file. In addition this
updates the recommended extensions for PHP to reflect what's shown in
Admin Panel > Dashboard > Information. Lastly, this updates various
links in the `README.md` and `UPGRADING.txt` files.

Author: JediKev

README.md

@@ -27,8 +27,9 @@ Requirements
   * MySQL database version 5.5 (or greater)
 
 ### Recommendations
-  * gd, gettext, imap, json, mbstring, and xml extensions for PHP
-  * APC module enabled and configured for PHP
+  * fileinfo, gd, gettext, imap, intl, json, mbstring, Zend OPcache, phar,
+    xml, xml-dom, and zip extensions for PHP
+  * APCu module enabled and configured for PHP
 
 Deployment
 ----------
@@ -58,33 +59,9 @@ Upgrading
 ---------
 osTicket supports upgrading from 1.6-rc1 and later versions. As with any
 upgrade, strongly consider a backup of your attachment files, database, and
-osTicket codebase before embarking on an upgrade.
-
-To trigger the update process, fetch the osTicket tarball from either
-the osTicket [github](http://github.com/osTicket/osTicket/releases) page
-or from the [osTicket website](https://osticket.com). Extract the tarball
-into the folder of your osTicket codebase. This can also be accomplished
-with the zip file, and a FTP client can of course be used to upload the new
-source code to your server.
-
-Any way you choose your adventure, when you have your codebase upgraded to
-osTicket-1.7, visit the /scp page of you ticketing system. The upgrader will
-be presented and will walk you through the rest of the process. (The couple
-clicks needed to go through the process are pretty boring to describe).
-
-### Upgrading from v1.6
-**WARNING**: If you are upgrading from osTicket 1.6, please ensure that all
-    your files in your upload folder are both readable and writable to your
-    http server software. Unreadable files will not be migrated to the
-    database during the upgrade and will be effectively lost.
-
-After upgrading, we recommend migrating your attachments to the database or
-to the new filesystem plugin. Use the `file` command-line applet to perform
-the migration.
-
-    php manage.php file migrate --backend=6 --to=D
-
-View the UPGRADING.txt file for other todo items to complete your upgrade.
+osTicket codebase before embarking on an upgrade. Please review our [Upgrade
+Guide](https://docs.osticket.com/en/latest/Getting%20Started/Upgrade%20and%20Migration.html)
+or the [UPGRADING.txt file](UPGRADING.txt) for upgrade instructions.
 
 Help
 ----

UPGRADING.txt

@@ -1,5 +1,33 @@
-Welcome to osTicket 1.7
-=======================
+Upgrading osTicket
+==================
+osTicket supports upgrading from 1.6-rc1 and later versions. As with any
+upgrade, strongly consider a backup of your attachment files, database, and
+osTicket codebase before embarking on an upgrade.
+
+To trigger the update process, fetch the osTicket tarball from either
+the osTicket [GitHub](https://github.com/osTicket/osTicket/releases) page
+or from the [osTicket website](https://osticket.com/download). Extract the tarball
+into the folder of your osTicket codebase. This can also be accomplished
+with the zip file, and a FTP client can of course be used to upload the new
+source code to your server.
+
+Any way you choose your adventure, when you have your codebase upgraded,
+visit the /scp page of you ticketing system. The upgrader will
+be presented and will walk you through the rest of the process. (The couple
+clicks needed to go through the process are pretty boring to describe).
+
+### Upgrading from v1.6
+**WARNING**: If you are upgrading from osTicket 1.6, please ensure that all
+    your files in your upload folder are both readable and writable to your
+    http server software. Unreadable files will not be migrated to the
+    database during the upgrade and will be effectively lost.
+
+After upgrading, we recommend migrating your attachments to the database or
+to the new filesystem plugin. Use the `file` command-line applet to perform
+the migration.
+
+    php manage.php file migrate --backend=6 --to=D
+
 Some tasks are better left to a system administrator rather than a mindless
 upgrade script. These are those remaining things that we'd rather you take
 care of: