Make page layout lookup code more robust when handling invalid docs

This prevents a null exception being thrown if the requested paragraph
has no details about the associated page style. As a second fallback,
if no style called "Standard" exists, this will fall back to the first
available master-page defined in the ODT.
Clarified ImageController function name
Remove duplicate code in OdfCanvas for finding the master page element
Cope with non-cm image dimensions

Style-related operations are slowly being moved towards px as the
default unit to improve consistency. Standardising getContentSize to
work in px rather than cm provides better re-use of CSSUnits as well.
Ignore test-generated ODTs
Provide better fallback mechanisms for Formatting.getContentSize

getContentSize will now always return a valid page size, falling back
to it's own hardcoded format if no valid one is found for the document
Merge pull request #463 from peitschie/master-page-nullfix

Make page layout lookup code more robust when handling invalid docs
Schedule UI updates using requestAnimationFrame rather than setTimeout

Using requestAnimationFrame ensures the callback is executed prior to
the next redraw, eliminating undesirable & highly visible flickers for
UI updates.

Fixes issue #491.
Reduce UI flicker on FF as well

FF doesn't execute requestAnimationFrame requests before it's next
repaint, causing flickering when performing some types of updates
(e.g., recomputing Style2CSS). To workaround this, sometimes we force
animation callbacks to redraw ourselves at certain points.

This fixes issue #491 on Firefox
Merge pull request #496 from peitschie/ui-flicker

Reduce UI flicker when performing CSS updates
Do not display <text:bibliography-source/>
Merge pull request #500 from kossebau/hideTextBibliographySource

Do not display <text:bibliography-source/>
make Webodf version a global property on the new namespace webodf
Add about dialog to editor component
fixup about dialog version
no need for nested requires with aboutdialog

fixup for Add about dialog to editor component
remove even more unneeded code structures

fixup for Add about dialog to editor component
fixup aboutdialog ko logo as external file
Show WebODF icon in Editor's About dialog button, name component "WebODF Text Editor" for now
Place About button to the very left, not right

to give it a fixed place also on toolbar shrinking