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/>
Don't crash if the requested range is outside the any document root

Fixes a crash when running the benchmark.
Merge pull request #497 from peitschie/benchmark-fix

Don't crash if the requested range is outside the any document root
Use a new ops.Canvas.getSizer instead of peeking
at the ancestry of the document root in SvgSelectionView.
Hide native selections only when virtual
selections are used.
Merge pull request #501 from adityab/native-selection-fallback

Re-enable selections for ODP and ODS documents
Use setStyle whenever selecting a new
style in the dialog.

This requires directly selecting a style
when cloning it, without waiting for onAdd.
Merge pull request #499 from adityab/pdialog

Load current style properties when opening dialog
Fix troublesome quotation of font-family name in CSS rule for embedded fonts