Kill the cat
Add the deprecated Claim handler functions to Property

Right now these deprecated functions don't fullfil their contract,
as the abstract Entity is not properly implementing them (which is
ok as these function are being phased out).

This is needed in order to actually make the Wikibase code that
still relies on these old functions work with properties (which
is something that used to work in the past when this code was still
in Entity).

Mid-term we will want to remove all usages of these functions and
then phase them out, but for now they should at least be properly
implemented (-> fullfiling their contract).

The code and the tests were copied from item, with only very minor
adjustments.
Fix border condition bug in BestStatementsFinder
Merge pull request #287 from wmde/BestStatementsFinder

Fix border condition bug in BestStatementsFinder
Update RELEASE-NOTES.md
Add Statement::newFromMainSnak

Split from https://github.com/wmde/WikibaseDataModel/pull/205
Add StatementList::getMainSnaks
Add StatementList::getWithPropertyId
Optimize StatementList construction from array
Drop optional Term array() parameter
[DNM] Make AliasGroup constructor parameter optional
Merge pull request #291 from wmde/termArray

Drop optional Term array() parameter
Remove Statement::newFromMainSnak
Merge pull request #285 from wmde/getMainSnaks

Added extra filter/map methods to StatementList
2.3.0 release
Merge pull request #294 from wmde/rel

2.3.0 release
Reworked all equals methods
Merge pull request #292 from wmde/aliasGroupNull

[DNM] Make AliasGroup constructor parameter optional
Merge pull request #249 from wmde/killacat

Kill the cat
Merge pull request #298 from wmde/equals

Reworked all equals methods