Implement shortcut keys using mousetrap library
Add keyboard shortcut help using ? key
Make / and s go different places for search
Get help modal working under straight theme
Ensure shortcut keys only fire on normal wiki page not edit page
Updated UserGuide ShortcutKeys page to show new facility
Merge pull request #400 from markhop/shortcut_keys

Shortcut keys
Avoid error by expecting an Integer after execution of FitNesseMain.

Return value can be null, in case we're not performing a command.
Fix spacing in execution log. Fixes #275.
Added hint for '?' functionality to page footer.