Prepare repository for transition to Gulp build

node_modules and dist folders ignored.
Use Gulp for Builds

Gulpfile and package.json, at the moment only concat task. TODO :
Linting, Uglify, Minify
Seal menu panel

Expose submitButton on ModifyMenu. In other modules referencing
ModifyMenu should now be able to select the submitButton specific to
this instance of the widget, not the buttons of multiple instances on
the page.

Prevent the menu container from blowing up vertically when using large
schema. The collision with widget instances below overlapped menus and
was unusable.
Seal menu bar

Expose XML and Text tabs, and also Undo/Redo menus.  This allows
specific instance selection instead of global JQuery selection by class
which did not work with multiple widget instances.
Change global select to instance select

Affected elements: Text / XML tabs and Submit Button on the ModifyMenu.