Add highlighting preference for Dynamic calls

The default colors for the new preferences are taken from already
existing highlighting classes. selectDynamic and updateDynamic are
highlighted as template vars, whereas applyDynamic and applyDynamicNamed
are highlighted as methods.

A new Dynamic category is introduced to the syntax coloring preference
page.
Remove needless information from preference page

It is already clear that the Scala preference page highlights Scala
symbols, no need to add this information again in the displayed name
of the ScalaSyntaxClass.