* wombat init fix:
- fix change from #339 which removed reiniting of wombat
- allow reiniting of wombat if inited via init_new_window_wombat()
- don't allow if reinited directly from <head>, as happened in document import
* tests: fix tests for 'new _WBWombat -> WombatInit' change
* wombat: window.frames optimization:
- since window.frames === window, no need for separate override!
- ensure init_new_window_wombat() is called on any returned window from object proxy
- store original wsgi SCRIPT_NAME (before collection path is pushed) in 'pywb.app_prefix' env var
- set 'pywb.host_prefix' via rewriterapp
- add 'static_prefix' jinja env global which defaults to 'pywb.host_prefix + pywb.app_prefix + static/'
- set 'static_prefix' to absolute url if available (to support proxy mode)
- update existing templates to use '{{ static_prefix }}' instead of '{{ host_prefix }}/{{ static_path }'
- update index.html to use pywb.app_prefix for collection links
- tests: add test_prefixed_deploy.py to ensure all paths are prefixed as expected
