terminator -x gets confused by --

[meator]

Describe the bug
terminator tries to handle -- after -x is specified, which is incorrect.

To Reproduce

terminator -x echo -- a

Expected behavior
Program working.

Instead, this happens:

usage: terminator [-h] [-R] [-v] [-m] [-M] [-f] [-b] [-H] [-T FORCEDTITLE] [--geometry GEOMETRY] [-e COMMAND] [-g CONFIG] [-j CONFIGJSON] [-x ...]
                  [--working-directory DIR] [-i FORCEDICON] [-r ROLE] [-l LAYOUT] [-s] [-p PROFILE] [-u] [-d] [--debug-classes DEBUG_CLASSES]
                  [--debug-methods DEBUG_METHODS] [--new-tab] [--toggle-visibility] [--unhide] [--list-profiles] [--list-layouts]
terminator: error: unrecognized arguments: -- a

Everything after -x should be execed verbatim without any additional argument parsing/handling.

The manpage says:

Runs the rest of the command line instead of your default shell or profile specified command.

Special handling of -- breaks this promise.

Desktop:

• OS or Linux Distribution: Void Linux
• Version: rolling release
• Display Technology: X11
• terminator version: reproducible on 2.1.3, 2.1.4 and on master

EDIT: Related to #939