Add link to Colors and Fonts preferece page in Hover preference page
Allow users to specify a font style for hovers in the CSS file

By default, the font that is configured in the "Colors and Fonts"
preference page will be used for the hovers. But if users configure a
font in the CSS file, it will be preferred over the preference value.
Correct HTML content of the "show type" functionality
Open Scala hover in "Show Tooltip Description" action

The Java hover was opened when this action was invoked. Now the Scala
hover is opened.
Show HTML hover when an annotation hover is focused
Configure information control creator when no SCU is available

The method `getInformationPresenter` is called not only for full editors
but also for "static" ones, i.e. the editors that are configured in the
preference pages. Because there exists no ScalaCompilationUnit for the
latter, the information presenter couldn't be correctly configured.

Now, a default information control creator is used, which is only used
for the "static" editors. All other editors (the editors for which a SCU
is available) use the non-default implementation.