First iteration of Moving to lua test format:
1)	Create regexp for checking if cmd is admin cmd or not. If it's not admin cmd, then prepend 'lua '.
1.1)	Add safe version of prev.command: admin(cmd, simple=True)
2)	Remove "lua " prefixes.
//TODO: rewrite TarantoolConnection(add execute_simple and modify for reconnection)
//TODO: add server format for pure lua tests (but it's needed to add delimiter for reading multiple lines)
//TODO: Rewrite some tests to pure lua
Also fix bugs, appeared after tt-gdb-fix:
1) 	Remove debug output
2) 	Add --gdb description
3) 	Return [self.binary]