GitModule minor refactoring

Open .git/config fixed
WorkingDirGitDir() replaced by GetGitDirectory()
` + AppSettings.PathSeparator.ToString() + ` replaced by `Path.Combine()`
FixPath replaced by ToPosixPath()
AppSettings.PathSeparator replaced by Path.DirectorySeparatorChar
` + Path.DirectorySeparatorChar` replaced by EnsureTrailingPathSeparator()
Implemented additional PathUtil methods
Merge branch 'feature/path-util'
Updated German translation

Change-Id: I2f29c83223379c890f8445808bfd671afba78e70

Update German translation missing t in Checkout fixing Checkou

Change-Id: Ic808d8756f66f1a612952dc7a0484fcdf92c4416
Removed duplicate Michael Benz (Copro) aka myelf from AboutBox

Change-Id: If28eea32dac0dd7a5f60fbb089b0be6579877563
Display new version and leave LinkLabel pointing to update URL

Change-Id: I3ac3945bfaed0b15f7f4b1f26655e48eb437ddf3
Merge pull request #2230 from Copro/master

Updated German translation and display new version information only instead of full URL
FormUpdates modified
msysgit url updated
MsysGit updated to version 1.9.0
Prefer preinstalled Putty
Two menu items moved to Tools menu
Trim entered directory
Moved menu items fixed
MsysGit version changed in installer