Full width documentation

Thanks @SvenDowideit for your suggestion in using the full width for the documentation while not changing the width of the Navigation. 

I've made some changes here to use a fixed width for the sidebar so it doesn't become too narrow for some lines. 

Not related, but required to keep a previous change from falling out: I've moved the .versionchanged, .versionadded, .versionmodified, in the .less file. - the .css is generated from that.

Please note that this PR supersedes PR #3226