Upgrade CodeMirror to 3.02
Matchhilight & autoCloseTags updates

CSS class changed needed for matchhilight and removed color setting
snippetFrame now unused, removed
2 new options set to autoCloseTags and highlightSelectionMatches
No longer setting thisCM.matchHighlight anymore
Set a if 1==2 condition on the previous (and quite ropey) code that did
autoclosing to stop it happening, will remove next.
Remove old close tag system, tweak highlights

Old and quite ropey close tag system removed in favour of the
CodeMirrror closetag addon
2 x classes to define highlighted text now forced to be white on blue
everywhere
Selected text forced to be white on blue
tagNestExceptions array removed

No longer used (was only used by the ropey close tag system, now
removed)