MGRS conversion fixes

[wcmatthysen]

Pull in fixes for MGRS coordinate conversion from upstream PR #157 of @gbburkhardt. The corresponding description from the PR is:

Fix two problems:

a) Index out of bounds error due to typo in convertMGRSToUPS; clearly the index should have been 1 instead of 12.
b) Conversions from geodetic to MGRS would fail for low southern latitudes (zone 0). Geotrans 3.7 has this problem fixed. The WorldWind conversion code was derived from NGA's Geotrans. Test case:
Lat: -89.345400 deg, Lon: -48.930600 deg ==> MGRS: AZN 45208 47747

See issue #160 in upstream repository as well.

[EMaksymenko]

By the way, I have ported this conversions earlier to Android code base.
So I probably need to copy this fixes to Android branch too.
Will wait the result.

WorldWindEarth/WorldWindAndroid#16

[wcmatthysen]

OK, the fix for this was done in PR #72. I'll take a look at porting the fixes to the Android code-base before closing this issue.

[PJHogan]

You guys are AMAZING! Nice work!

[wcmatthysen]

The fixes are now ported to the Android code-base. So, I guess we can close this issue.