Resource makeFull

[SystemFw]

Although there are a few open questions, I think this is ready for an initial review.
The most relevant files are Resource, Semaphore, and the relative tests.

Summary of the changes:

• Resource is invariant in F
• No more preinterpretation, and different nodes: Allocate, Eval, Pure, Bind
• Resource can now express interruptible acquires
• Fixed a bug in bracketFull which allowed interruptible releases
• liftF is deprecated in favour of eval
• Semaphore has a new implementation. Hopefully it's clearer, although the underlying idea remains complex (necessarily so)
• Resource.mapK requires a MonadCancel constraint on both source and destination effect, and it cannot be avoided.
• Various cleanups, simplifications, scaladoc, etc.

Open questions:

• Resource.mapK requires a MonadCancel[F, Throwable] on both source and destination effects, which is problematic for Semaphore, which currently only takes a GenConcurrent[F, _]. I've tried quite a few things, one thing still left to try though is having mapK take MonadCancel[F, _] and MonadCancel[G, _], and see how that goes (skeptical, but we'll see). This appears to work.
• I think that as constructed, allowFull can be engineered to build a Resource with interruptible release (makeFull cannot). Not quite sure if we want to tackle that, or just say "don't do that". Fixed in bracketFull.
• I've left liftK with the current name, rather than evalK, since consistency with cats for that sort of operation seems more important (whereas for liftF/eval, consistency with fs2 is). Let me know if you have a different view, and evalK should be introduced instead.