Add Python-based AccurateRip v2 checksum with range support.

This performs the slow, brute-force approach but does pass the unit tests.
Update trackverify/cd2track with AccurateRip v2 support.

Version 2 output is reported before version 1,
and version 2 checksum is default if nothing is found.
Add more optimized Python-based AccurateRip v2 calculation.
Unify AccurateRip checksummers into single object.

Both V1 and V2 have very similar algorithms so it make sense
not to do a lot of extra work during calculation.
Unify AccurateRip checksums into single object.
Add AccurateRip V2 support.

Unlike V1, this does *not* work on over a range of samples with offset detection;
it only verifies the stream at offset 0 and if that doesn't match
utilities fall back to checking version 1 and offsets.

Though the math seems simple enough, I've yet to deduce a way to
calculate checksum deltas needed for sliding the "window" in constant time,
so this will have to do.

Simplify a lot of the AccurateRip routines in the process to
leave fewer places for bugs to hide.
Minor AccurateRip V2 optimization.

Speedup calculation by storing the checksum as a delta of the V1 checksum.
Display message if pkg-config cannot be found to probe for libraries.