Use GWT ClientBundle to inject CSS rules

From the GWT docs
(http://www.gwtproject.org/doc/latest/DevGuideUiCss.html#cssfiles),
this is the preferred way to add custom CSS. Using a <link> in WMT.html
is deprecated.
Use CSS selector specificity to force custom rules

The bootstrap.min.css rules are overriding the custom rules for WMT.
Making the WMT rules more specific forces them to be used instead.

Still need to fix contents of DialogBoxen.
Add tooltip methods to the DataManager
Apply GWT-Bootstrap tooltips to ModelActionPanel

A bug -- the tooltip isn't dismissed when a GWT DialogBox is shown
after clicking a button. The workaround is to include a reference to
the tooltip in the button's ClickHandler, where the tooltip's hide
method can be called.