Add optional window name when loading windows

This turns windows into templates making them reusable in the same or multiple sessions.
When creating windows I omit both the window_root and the name on new window. Now I can create multiples of these and have them named what I want them. I also call window_root prior to load_window.

````
session_root "~/work/projects/MASSIVE_APP"
if initialize_session "MASSIVE_APP"; then
  window_root "./module_1"
  load_window "dev" "mod1"
  window_root "./module_2"
  load_window "dev" "mod2" 
  window_root "./module_3"
  load_window "dev" "mod3"
  select_window 1
fi
finalize_and_go_to_session
````

Example Window
````
new_window
split_v 50
split_h 50
run_cmd "vim ." 1
run_cmd "grunt watch" 2
run_cmd "git status" 3
select_pane  1
````