Switch the main codebase to use mousetrap

Link hints still uses keyboardUtils, but the main vimari codebase uses
mousetrap.

Additionally, and importantly, it also adds a setting for the modifier
key. Then, we get the option to turn off the modifier virtually for
free.
Edit mousetrap to restore previous ctrl behavior

Prior to integrating mousetrap, ctrl commands were always available,
ex. you could ctrl-f in an input. Since mousetrap disables itself for
inputs, this behavior was regressed.

This patches mousetrap to allow the event to trigger in an input
if it has a modifier key. If mousetrap sticks around in this codebase,
a more generic solution should be attempted to be pushed upstream to
mousetrap.
Restore ability to open links in new tab

This behavior was accidentally removed when switching to mousetrap;
fixed.
Fix some odd edge case behavior

At some point I determined keypress and keydown didn't work, and needed
to hook into keyup. This is not true anymore, and this patch makes
things work smoothly.

Note that keypress ignores meta keys, which breaks the ability to not
have a modifier prefix for commands. Thus, we do need to use keydown.
Changed author to Various, removed CTRL- from settings text