mathjax iframe injection
Merge branch 'develop' into feature/mathjax

Conflicts:
	js/views/reader_view.js
Merge branch 'develop' into feature/mathjax

Conflicts:
	js/views/reader_view.js
added mathjax call
loading mathjax on demand
robustify code against null paginationInfo + adjusted edge-case for RTL flow rectangle detection method
restore reading position when resize (upper left corner, so approximate)
fix / workaround for  WebKit / Chromium regression bug with CSS columns and vertical writing mode + Right To Left page progression direction
typo for page lookup
fixed column pagination resize
minor: arithmetic test for column width
reflow trigger for column visiblity check (e.g. direct TOC link into column index page)
Implement iframe content, script, and reading system object injection.
Merge branch 'feature/iframe_injection' into feature/mathjax

Conflicts:
	js/views/reader_view.js
IE support for vertical writing mode
Pass mathjax url to iframe loader.
Inject mathjax script
Disable old mathjax injector function for now.
Don't re-use the same iframe element for reflowable layouts.
Instead destroy and create one every spine item change.
This fixes an issue in where MathJax does not reinitialize on spine item document changes.
Inject reading system object before writing to the iframe DOM.
Remove previous attempt at reading system injection.