Set VS2012 ShellEx project tools version to 110.

 - This allows the app to be built on systems w/o VS2010 installed.
Change v110 to v110_xp to support windows xp.
Merge pull request #1512 from DanRigby/FixVS2012ShellExtensionsToolsVersion

Set VS2012 ShellEx project tools version to 110.