Revert "Revert "Changes build process so that both .Net4 and .Net45 libs are built""

This reverts commit aa31ae86c57378f17c12cb416112a70dc5349f86.
Removing unnecessary transform
Shaves off a few seconds off unit tests by loading the images just once
Removes a few images to gain a few seconds during unit tests
Refactors unit tests so that the resulting images are actually tested
Changes unit tests to use FluentAssertions and tests a bunch more stuff (doesn't pass the tests)
Resets the image factories each time the collection is called
Refactors the huge copypastas with nicer loops
Merge branch 'unit-tests' of github.com:cosmo0/ImageProcessor into unit-tests