* Implemented signature sorting for imports, use namespaces,
variables, functions, classes and interfaces, plus associated
metadata. This should speed up compile times when the items listed
above are moved around.
* Implemented human readable option with signature generation. Human
readable is only on when keepGeneratedSignatures is true. When it's
off, only essential info is added to the signature and abbreviations
are used for keywords. This should speed up compile times and
reduce compiler memory use.
tests Passed: checkintests, compilerperformance (the four failing
invalidation tests should be removed)