VS2014 support in VSExtension

Ability to install/uninstall vsix packages through VsixPackage element from the VSExtension.

Very straight forward following of the old code as the vsix installation did not change from VS2013 to VS2014.
Could you help me more please? I believe the property VS_VSIX_INSTALLER_PATH has not been renamed, it has been moved, Following the same convention/logic that has been used prior to my changes.