Add more activation locations

A few more places (classes) could use Syntax Highlighting:

• XWiki.UIExtension (wiki mode)
• XWiki.SchedulerJobClass (wiki mode)
• XWiki.ConfigurableClass (wiki mode)
• XWiki.ComponentMethodClass (doc syntax mode)

Other places where it's problematic to add it are:

• Skin file overrides (hard to tell which mode to enable, since it depends on the overridden file)
• Flamingo themes (hard to enable the LESS mode in object editor, because it's a subtype/mimetype exposed by the main css mode; also, in inline edit, the textarea in Advanced is hidden)