parentElement is not defined on non-Element nodes in IE10

To have a "blanket rule", just use parentNode everywhere to prevent future problems,
as it is equivalent to parentElement for all practical usages.
navigator.language does not exist on IE10, so check for it as well
Handle IE10 obv. destructing event objects once the event handler is done
Merge pull request #718 from kossebau/smallFixesForIE10

Small fixes for IE10
Be more verbose in the About dialog of ViewerJS, not on toolbar
Merge pull request #719 from kossebau/moreInfoInViewerJSAboutDialog

Be more verbose in the About dialog of ViewerJS, not on toolbar
Add ChangeLog.md
Merge pull request #721 from kossebau/addChangeLog.md

Add ChangeLog.md
Enable reaching the Viewer's About dialog close button in small windows
Clean-up np longer needed build target viewerbuilddir-target
Merge pull request #716 from kossebau/fixViewerAboutDialogUncloseable

Enable reaching the Viewer's About dialog close button in small windows
Fix broken copying of dijit*.css
Merge pull request #725 from kossebau/fixBrokenDijitCopying

Fix broken copying of dijit*.css
Re-implement navigate-to-line-boundary cursor movement
Re-implement navigate-by-line cursor movement
Re-implement up/down movements caching the last caret X position

When navigating vi the up/down arrow keys, the user often wants to move
multiple lines in sequence (e.g., to visually place the caret in one of
the following lines). To stop the caret suddenly jumping to the left
side of the page when crossing an empty paragraph, the caret's X position
will be stored and re-used by subsequent up/down movement for up to 2s
after navigating by line.

Any other operations performed by the local user (e.g., cursor movement
to the left or right), or edit operations by collaborative users will
immediately clear the stored X position.
Merge pull request #609 from peitschie/line-boundaries

Rewrite of line boundary movement actions
Fix outline elements sneak from master pages into the shadow copies
Merge pull request #728 from kossebau/fixOutlineElementsSlippingIntoSlides

Fix outline elements sneak from master pages into the shadow copies
Add changelog entry for line boundary navigation fixes