[de] improve some speller suggestions
tiny cleanup: remove priority from toString() output as it's not used by LT anyway
If you develop your own rules that are not part of LT you can now add external="yes" to your categories to prevent the rule link to community.languagetool.org from appearing in our stand-alone GUI (the link would not work for rules that are not part of the main distribution of LT)
deprecate the Category constructors with priority, as the priority value isn't used at all
tiny code cleanup: use constants
adding ITS 2.0 localization quality issue type "non-conformance", which was missing from the list (see http://www.w3.org/International/multilingualweb/lt/drafts/its20/its20.html#lqissue-typevalues)