Add some styling to the table of contents on optional plugins page.
Fix #441: Update new split tab view position on the UI thread

Moved position update onto the UI thread so it is executed when
the UI reconfiguration is complete. The view position is adjusted
to match observable VIM behaviour -- keeping the cursor at a relative
offset to the top of the split.
Merge pull request #455 from igrekster/fix-441

Fix #441: Update new split tab view position on the UI thread
Update unstable update site.
Allow macro or mapping containing <TAB> key.

The tab is inserted straight to Eclipse which will then place a literal
tab or the equivalent number of spaces according to the Eclipse settings
of the current editor.

This does mean the Vrapper tabstop options are ignored, but at the same
time the user will see the same kind of tab as he would if placing it in
insert.

Fixes #454.
Merge pull request #456 from albertdev/tab-key-in-macro

Allow macro or mapping containing <TAB> key.
Update unstable update site.
Make surrounds editortype-specific.

As discussed in https://github.com/vrapper/vrapper/pull/390/files#r10871256

Instead of keeping the delimiters in a static variable, use a regular
so that it is unique for each editortype (or more specifically, for
each SurroundStateProvider instance).
Update unstable update site.
Use non-null selection marks if possible.

The indentation code sometimes clobbers the last selection marks, but
most times the end mark is still valid. As it is the most useful of
the two, don't reset it to its former offset value but use it as is.

Work for #446.
Add table of contents to Configuration page of the docs.
Prevent screen flicker during selection changes.

Since the selection change code first moves the caret and then restores
the selection, changing the selection with "line down" would continously
flash the screen.

Disabling redraw during such a change allows for a smoother experience.
Document range for 'run external' cmd line.

Add a few examples for good measure.
Fix #459.  Add support for ":command" to define custom command-line
commands.
Update unstable update site.
Simplify implementation for #459.
Update unstable update site.
Fix #150.  Don't do a softtabdelete if the backspace is virtual.  `imap
jj <esc>` sends a virtual backspace but handleKey0 won't pass the key to
the underlying editor if handleKey returns false.
Update unstable update site.
Cleanup some work on #459.