Right click menu takes a long time with large code bases

[carpenterjc]

With SublimeAutoPEP8 it can take a very long time for right click context menu to appear when you right click on folders, to for example search for files.

Steps to reproduce:

1. With a codebase of 20k files or more loaded in the side bar. There may need to be some python scripts somewhere, but mostly lots of c++ files.
2. Right-click on a folder in the sidebar, it takes less than 200ms to show.
3. Install Auto-pep 8 right click now take a long time to show > 5-10 seconds.
4. Rename the file Side Bar.sublime-menu to Side Bar.sublime-menux, goes back to 200ms. Note: You can toggle this behavior on on off by renaming this file.

[wistful]

different behaviour for right click context menu:
New option file_menu_behaviour:

• always: menu appears always, even folder doesn't contain *.py files
• never: menu never appears
• ifneed: default value, menu appears only if path or childs contain *.py file

New option file_menu_search_depth (default 3) defines max search depth for ifneed mode