Allow users to press enter in autocomplete by default. Close #1296

Not being able to press enter in all contexts by default (including autocompletion) is surprising.
Users can still select a completion with tab.
Mention license in readme, close #973
Adjust contributing wording to avoid any misleading wording, close #1614
Fixed couple of compile-time warnings #1658
Fixed couple of compile warnings
Fixed couple of compile-time warnings #1658
Bring back some functions, that might broke inner API
Encourage users to go the mailing list for questions

A number of issues I've addressed in the past weeks were questions that had a better
chance being answered in the mailing list than being a github issue.
Most recently #1704. Also added a section on what to include on bug reports.
Fix remaining warnings that can be fixed

Outstanding warning is caused by fetch. Did end up removing populate
as it referred to a nonexistant function and couldn't have worked since
it was imported
Fix inline-exception warning properly
Merge branch 'pr/1698'
ibdknox.css: fix tab coloring

To see what this commit does do following:
1. Set editor theme to "ibdknox".
2. In new-dark.css change var-highlight-fg to #0f0. Save new-dark.css.
3. Connect to 'Light Table UI'.
4. Open multiple editors, change content in one of them. Don't save!
5. Switch between editors, notice color changes in tab names.
6. Undo/redo the change introduced by this commit. Goto step 5.