Merge stx to itx

I created clocksi_static_tx_coord_fsm to receive all operations from clients and issue these operation one by one to interactive_static_tx_coord_fsm.

In the append function of floppy.erl, I added the user time to the call of clocksi_execute_tx(). The time is added in order to avoid an anomaly caused by the snapshot time treatment of clocksi_interactive_tx_coord_fsm. I will describes this in detail in issues.