Persistence support + numerous fixes and improvements

!!!NOTE!!! Do not merge this PR, WIP.

As to @lstrojny  request, https://github.com/pdezwart/php-amqp/issues/122#issuecomment-55711669.

Major changes and improvements list - https://github.com/pdezwart/php-amqp/issues/122#issuecomment-54773945

TODO:

- [ ] squash commits
- [ ] add phpt tests to cover added methods