Fix crash when certain list style elements are not present.

Specifically:

1. No style:list-level-properties is present.
2. No style:list-level-label-alignment child of that is present.
   In this case, it simply falls back to default zero margins and
   bullet widths.

Previously this would simply not load documents which did not come
with this optional element in a list style.

Layout tests and CSS generation tests are added for both cases.
Merge pull request #533 from adityab/list-level-props-optional

Fix crash when no style:list-level-properties is present
Refactor calculation of CSS content for lists

Moved the processing of the list style to get the content rule into a
separate method so it can be re used for continue list styles. Also
ensured that the new getContentRule function returns a complete rule with
the semicolon on the end.
Support multi level list numbering

Implemented a changed list counter setup where each list level has its own
counter. This is to support behaviour defined where you can display only a
subset of the list numbers.

This is defined here:
http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#__RefHeading__1418890_253892949
Provide each text:list with a unique CSS counter

Giving each list a unique counter allows us to implement continued
numbering functionality while avoiding unexpected numbering due to how CSS
counter values are scoped to an elements sibilings or children.
Implement continued numbering

This adds support for the text:continue-numbering and text:continue-list
attributes. The text:continue-numbering attribute specifies whether to
continue the immediately preceding list if it has the same style.

http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#attribute-text_continue-numbering

The text:continue-list attribute specifes the unique identifier of a list
to continue numbering from in the document. These must also have the same
style.

http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part1.html#attribute-text_continue-list

https://tools.oasis-open.org/issues/browse/OFFICE-3558
Remove dead code from OdfCanvas and OdfUtils

The removed code was intended to implement continue list functionality.
However this code no longer worked due to a regression introduced in commit 3ae9e0c.

As I have refactored this area and implemented the continue list
functionality in the new list styles class this old code is no longer
required.

The removed code in OdfCanvas also made use of the
getFirstNonWhitespaceChild function in OdfUtils and the removed code was
the last remaining usage of it. As it is preferable to make use of DOM API
calls which give us the desired behaviour such as
element.firstElementChild I have removed this function.
Added tests for continued and multi level lists

Added unit tests for the continue lists and added some examples of
continued and multi level lists to visual-tests.fodt
Merge pull request #565 from satsuper/list-numbering

Various list numbering improvements
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