Fix bug where ODP page numbers would be hidden.

In a9c4f35245d058982a4366d826c42afb41d12ba6,
the regex for checking whether the attribute
presentation:class matches an approved set
of values had an extra ' at the end, which
meant that frames with class 'page-number'
were being dropped.
This is now fixed.
Merge pull request #254 from adityab/pagenumber-fix

Fix bug where ODP page numbers would be hidden.
Coding style fix: indentation was off by -1
Restore the end point of selection range to where it was initially after
splitting boundaries.

Given the following selection <p>a[bcd]<span>efg</span></p> calling the
splitBoundaries at the moment moves the end point of selection to immediately after opening span <p>a[bcd<span>]efg</span></p>
this causes getTextElements (passing includePartial = true) to return
both "bcd" and "efg" which is incorrect.
Add support for adding and removing text hyperlinks
Added editor buttons for modifying or deleting hyperlinks