Add initial implementation of Javascript Quests (*.jsq)

This works by reading a .jsq file as a .quest file up until the toggle
string, ">>>" at the beginning of a line. From then on, the Javascript
parser will take over.

Additionally, provides Javascript helper funtions (including
util.require(), which allows loading of other .js files from the
resource directory/jslib).

Signed-off-by: Robert Xu <robxu9@gmail.com>