Rewrite of CPR algorithms

[mrksngl]

Note: this is a API breaking change!

API

• class CompactPositionReporting deleted. Its two static methods (local and global decoding) are now part of CPREncodedPosition
• Constructor of CPREncodedPosition has a new flag

It would be possible to supply @Deprecated versions for those 3 changes, but I don't think that anyone used those methods directly. Also any broken calls can easily be ported to the new API.

Changes

Not altering behavior

• CPR was rewritten using fixed point integer math arithmetic which gives provably the same results of the standard's algorithm (which operates on reals)
• speedup of the NL function
• speedup for surface positions
• speedup of minor special cases

All changes are done by mathematical equivalences and do not change the algorithms, except for cases where the old implementation produced wrong results due to limited precision (if any).

All tests have been adapted (API wise) and pass.

Altering behavior

• Tests on timestamps for global decoding is now already part of method decodeGlobal, because the constraints on timestamps is actually a prerequisite of the algorithm to produce correct results.
  It is still possible to disable those tests having timestamp = null but it is not encouraged (nor used by libadsb).
• Maximum gaps on timestamps are refined and now follow the standard
• Global decoding will no longer emit invalid positions (e.g. latittude > 90) but rather return null (i.e. global decoding fails then)

Final note

The decodePosition method has been left as-is (some tests moved but are still all in effect).
The reasonable tests are still not compliant with // see A.1.7.10.2 of DO-260B, so you might want to change that comment. The tests are rather inspired by the standard.

[fixje]

It would be possible to supply @deprecated versions for those 3 changes, but I don't think that anyone used those methods directly. Also any broken calls can easily be ported to the new API.

ACK. The next release will already have breaking API changes. No need to keep old cruft.

[mrksngl]

Additional Changes

• static factory methods
• mandatory timestamps for CPR. Will tackle upstream timestamps in a future PR
• additional unit tests on timestamp gaps

[fixje]

LGTM now