Improved separation between CKMon2Htm and CKMonEntryPageWriter. (...)

- Moved most static utilities into a static HtmUtils class.
- CkmonHtmlWriter is now CKMonEntryPageWriter.
- CKMonEntryPageWriter now handles writing of open group headers/footers and large next/prev buttons.
- CKMonEntryPageWriter now has access to the monitor index, to ease navigation for the current monitor.