Add netfx 4.5.2 support to NetFxExtension
Unify BuilderBase across test projects

There were basically duplicate definitions of builder classes in both WixToolTests and WixTests. This change consolidates them.
Merge pull request #33 from gordonmcshane/NetFxExtension-4.5.2-support

Add netfx 4.5.2 support to NetFxExtension
Merge pull request #81 from heaths/testfixes

Unify BuilderBase across test projects