qc: Move helper instanes to Extra_Arbitrary module

These should eventually make their way upstream.
qc: Fix range of arbitrary_uint{16,32,64}

Previously these were only generating maximum values of 2^(n + 1) - 2.
qc: Add serveral instances for SDN_Types
qc: fix bug in arbitrary_uint48 from refactor
qc: Give arbitrary modules better names
qc: Add arbitrary instance for uint64
Merge branch 'master' into qc-range

Conflicts:
	_oasis
	quickcheck/Arbitrary_OpenFlow0x01.mli
	quickcheck/quickcheck.mllib
	setup.ml
Merge pull request #64 from frenetic-lang/qc-range

QuickCheck Reorg and Range Expansion