Remove core/multipass, main, wip folder

[tsherif]

Second round of cleanup:

• Remove core/multipass classes. The ones that are used in the glfx example have been moved there so the example still works.
• Remove effects/experimental/passes. They were unused and depended on core/multipass
• Remove main module and fix tests that were using it.
• Remove glfx module (it was just an alias for effects)
• Remove wip folder

Core Bundle Size

Before	After	Improvement
296kB	291kB	5kB (1%)

[coveralls]

Coverage decreased (-1.5%) to 61.553% when pulling c6ee9e8 on multipass-cleanup into 1885867 on master.