Clean up Avatar styling and remove !important tags from webodf.css

Historically, the avatar styling was split between the avatar class,
webodf.css and the editor's own CSS. This now all lives within WebODF,
so the !important tags are no longer necessary as the style attributes
being set on the handle and image elements can simply be removed.
Keep IME character selection menu in one place during composition

f78a30a introduced a regression that caused the IME menu to appear to
follow the caret across the screen as new characters are entered, rather
than remaining anchored at the beginning of the composed text.

This patch adds some width calculations, and aligns parts of the caret
overlay to either left or right side of the container. As the caret
overlay is widened, the event trap will remain fixed to the left, and the
caret + avatar handle will remain fixed to the right.
Redraw the caret if the composition sequence is aborted

If the user abandons the composition sequence (e.g., by pressing the
escape key before choosing which word to input), the text is cleared and
no operations or other updates are required. Subscribe to this event as
well to ensure the caret is redrawn back at the proper location.
Remove unnecessary eventTrap CSS rules

The event trap is no longer made visible during composition. As a result,
the overflow and width settings are no longer required, and the height is
never overridden.
Add changelog entry for fixes
Merge pull request #613 from peitschie/ime-caret

Keep IME character selection menu in one place during composition