3.0.0-RC1

Merge pull request #41 from horde/fix/ActiveSync_loops
fix(activesync): consolidate state constants and document initial-sync ACK
fix(ActiveSync): force KEYMISMATCH when loading corrupt sync_data
Fix: Filename typo
fix(ActiveSync): harden state persist against races and sync_data corruption
docs(ActiveSync): clarify row lock behavior and sendNextChange contract
fix(activesync): serialize parallel state access with SQL and Mongo row locks
fix(activesync): repair initial sync, corrupt state, and nested MIME export
fix(activesync): reject corrupt collection sync_data on load and save
fix(activesync): separate PING watermark from SYNC modseq to stop iOS mail loops
refactor(ActiveSync): use HordeString instead of Horde_String in METHOD handling
Update MeetingRequest.php
Simplify method retrieval in fromvEvent
Refactor METHOD handling in EasMessageBuilder
fix(Iterator): use void return type for next() instead of ReturnTypeWillChange
fix(Device): restore isset guard for OS property access
Fix php and phpunit deprecations