Use GitVersion to generate unique prerelease tags

We won't use semver until v2.0, so until then we aren't taking full
advantage of GitVersion.

Author: carolynvs

build/build.proj

@@ -3,7 +3,11 @@
 
   <PropertyGroup>
     <Configuration>Debug</Configuration>
-    <Version>1.5.0.1-beta1</Version>
+
+    <!-- Note: We won't start using semver until v2 -->
+    <PrereleaseTag Condition=" '$(bamboo_GitVersion_BuildMetadata)' != '' ">-beta$(bamboo_GitVersion_BuildMetadata)</PrereleaseTag>
+    <PrereleaseTag Condition=" '$(bamboo_GitVersion_BuildMetadata)' == '' ">-SNAPSHOT</PrereleaseTag>
+    <Version>1.5.0.1$(PrereleaseTag)</Version>
 
     <ILMerge>$(MSBuildThisFileDirectory.Replace('build\','src'))\packages\ILMerge.2.14.1208\tools\ILMerge.exe</ILMerge>
     <NuGet>$(LocalAppData)\NuGet\NuGet.exe</NuGet>
@@ -25,6 +29,7 @@
   </Target>
 
   <Target Name="Build" DependsOnTargets="RestorePackages">
+    <Message Text="Building version $(Version)..." />
     <Exec Command="$(MSBuild) ..\src\openstack.net.sln /p:Configuration=$(Configuration) /nologo /v:minimal" />
   </Target>