Tweak appearance of tags editor

Making it a bit more like http://aehlke.github.io/tag-it/
Change link for ribbon to ReleaseHistory
Docs updates
Make sure tags are in alphabetical order in the view template

Fixes #242
Add docs about the release process

Mainly for me, beause I keep getting it wrong
Version update
Update version number and ribbon colour ready for the next release
Fixed small but important bug that prevented downloading an empty wiki
Version update
Update version number and ribbon colour for alpha-18
Clarify location of license files
sign contributor license agreement