Add docs for first-class document features, split API section
into subsections to make it easier to read.

 - Move a lot of methods from the CodeMirror to the Doc prototype
 - Allow getting, attaching, and copying of Doc objects
 - Add linkedDoc to create documents that stay in sync
 - Allow such linked docs to be sub-view on their parent
 - Rewrite history handling
 - Remove the concept of a view

Documentation still failing.

Issue #1166

Append image to wrapper. No more appending to document.
Works with multiple editors. Tested: 3 editors beneath each other on 1 page.

Closes #1168

Add Opera Mobile UA to the mobile list.

Issue #1163

Issue #1164

Issue #1160

Closes #1161

It would occasionally mark lines as hidden that were needed to display
parts of other lines.

Issue #1161

* mysql & mariadb:
** .21 syntax
** .table_name syntax
** added keywords
* MIMEs define their operatorChars
* MIMEs have a support prop
* use spaces as tab in index.html for consistency
* some return false -> null
* more comments

They'd exhibit the same infinite traversal behavior mentioned in
#1155

Closes #1149

Even when a subset is selected.

Tests are now specified in a less redundant format, and should be
easier to read and write.

Issue #1151

Closes #1148

It damages parent-child relationships in subnodes, which we might still
need later.

Closes #1147

Widget handles now have .clear() and .changed() methods. The second informs CodeMirror
that the widget changed, and causes it to recompute the line height for the widget's
line.

Fixes some sloppiness in the tracking of widget heights.

Due to changed line heights, the rendered content might not reach to
the viewport bottom.

Issue #1147

Set correct year in license.