added split_hl and split_hl and split_vl which split with a count of
columns/lines instead of by percentage, and clock which starts
clock-mode. Comments for each added.
This means that "init" session layouts can now be used to start and/or
re-attach to your main session.
Personally I have a "main" session layout with a couple of default
windows. I can now either start that session, or re-attach to it from
outside of Tmux by just running `tmuxifier s main`, instead of manually
creating a session named "main" and then loading my windows into it.
Instead of assuming that the default created window in a new session has
a index of `0`, we now check window index for the session with Tmux's
list-windows command.
Additionally, the default window is now moved to index `999` instead of
`99`, cause I'm paranoid and probably stupid :)
After some experimentation it turns out that if input to send-keys is
not a known key sequence like `C-m` or `C-l` for example, it it
automatically treated as literal input.
Negating the need to use it and hence check if it's supported.
