Remove QGL from PyQLab.

[blakejohnson]

QGL has moved to https://github.com/BBN-Q/QGL. The common JSON library manipulation code is now at https://github.com/BBN-Q/JSONLibraryUtils.

Still TODO before merging this:

• [x] Add JSONLibraryUtils submodule and remove that code from here
• [x] Write a migrator for the revised ChannelLibrary schema.
• [x] Update the settings validators
• [ ] User testing (we don't currently have automated GUI testing).

[blakejohnson]

Well, I should fix the broken unit tests, but otherwise I think this is ready to go modulo some user testing.

[caryan]

@blakejohnson do we need to ensure both QGL and PyQLab configs are pointing to the same channel library file?