3.0.0-RC3

Merge pull request #50 from horde/fix/find_meetinginvitation
feat(activesync): add EAS 16 Find and improve meeting invitation RSVP support
test: address review feedback on PSR-4 layout
chore: metadata
test: Modernize test suite to PSR-4 layout and remove dependency on Horde_Test
refactor(activesync): use Horde\Util\HordeString PSR-4
fix(activesync): emit correct FolderType on ItemOperations fetch
fix(activesync): parse calendar InstanceId as Horde_Date on SYNC_MODIFY
Merge pull request #47 from horde/fix/find_result_itemOperation
Merge pull request #46 from horde/fix/FIND_skip-nonexistent_messages
fix(activesync): return object-not-found for deleted ItemOperations fetches
fix(activesync): skip missing messages in Find results