* Tidy up and add txid at beginning of transaction
* Add ffi crate and new_store function
* Add register and unregister observer FFI, Store and Conn functions.
Also add android logging facilities
* Add function for fetching entids for attribute strings
* Add functions for iterating through TxReports
* Add sync to ffi boundary
* Move Extern types from submodule to lib in FFI.
For some reason, if these types are in a submodule, even if they are publically used, the functions inside the FFI are not found in
Android. Works for iOS though. To be investigated later....
* Return to passing TxReports to observer function.
Also, remove some debug
* Expose DateTime and Utc publically
* Use Store in observer tests
