WIXBUG:4561 - update WixCop to migrate v3 source code to v4.0.
Rename WixCop's Inspector to Converter in Wix.dll.

WixCop named it's code converter "Inspectors" and Wix.dll provided an
IInspector extensibility point. We are moving the WixCop Inspector
to Wix.dll to get access to some internal methods thus the rename was
necessary to avoid confusion.
Remove unused namespaces.
Generate anonymous File/@Id same as in WiX v3.
Use standard WiX toolset messaging infrastructure for WixCop.
Remove unused wixcop test project.
Merge pull request #60 from firegiant/4561-migration

WIXBUG:4561 - update WixCop to migrate v3 source code to v4.0.