improve code editor component

[mispp]

now, code editor is just extension of qplaintextedit, which is ok, but following features need a lot more work:

• improvement of the syntax highlight for multiline comments
• row numbers
• vertical lines on the right (80 chars)
• code completion
• code folding (not really that necessery)

these features are integrated into qscintilla and ktexteditor, so their usage might be the way to go.

• for ktexteditor switch to cmake is needed
• for qscintilla settings and color selection for highlight type needs to be further investigated, also how to get 'query at cursor' to submit with ctrl-enter. qscintilla is taken fro sqlitebrowser for testing and is in a separate branch