Votive support for VS2015

- Update WiX version numbers to v3.10
- Add/register Votive for VS2015 (plus VS2013, VS2012, and VS2010).
- Fix MSBuild targets for v3.10 installation directory.
- Also fix setup to add missing schema files.
Shouldn't "Votive Package for Visual Studio 2013" be "Votive Package for Visual Studio 2015" here?