TinyMCE upgrade (v. 4.1.7)

Merged back from a working implementation in v. 3.1.8. There are still some things to check/fix: ssmacron + spellchecker.

It's a start. I might have missed all kinds off dependencies, but it's working quite nicely as far as I can tell.

PS. Some more styling was changed after running compass after adding some tinyMCE specific stuff.
PPS. Perhaps also applicable for the 3.1 branch (as I got it working for that branch)? I don't think I'm breaking anything, but the options available for HtmlEditorConfig will change of course.