Removed DivertFilesFilter, which was conspicuously incomplete and
not referenced anywhere (even in .xml config files). Discovered during yellow-triangle-removal
because it had an unused variable in it.
Suppressed some variable-not-used messages where it seems likely
that a bigger fix (that uses the variable) will be applied later anyway. TestAPISpecExtractsPropertyExpiryTimes
had lots of these, eliminated by writing the missing tests in a different way.
Cleaned up half-done URIUtils testing, put in a parameterised
list of cases for resolution against request URI and API base.
Deprecated EXTRAS and replaced by ELDA_API, likewise removed
vocab/extras.ttl and renamed to elda_api.ttl. Replaced in-Elda uses of EXTRAS with ELDA_API.
EXTRAS extends ELDA_API so that it continues to work. ELDA_API extends API so that we don't
need to juggle two class names for the API-like proeprties.