Some work on the editor stuff:

- Move some of the HTML mode handling into KMeditor, remove duplicated code elsewhere
- Add some more api dox to KMeditor
- Don't enable HTML mode by default
- Fix fixed font option
- Fix lists - they can now be removed again and the combobox is properly updated
- Fix incorrect missing attachment detection
- Remove and move around some other stuff
- Move init() into the private class of KMeditor
- Some style/kdebug fixes