Pull Request for Issue # .

Summary of Changes

Title says it all

Change log:

[Fixed] - bug where the SaxParser would run out of memory on very large documents.
[Fixed] - bug with formatting like font size wasn't applied to del elements.
[Fixed] - bug where various api calls would be throwing exceptions if they where invoked on a removed editor instance.
[Fixed] - bug where the branding position would be incorrect if the editor was inside a hidden tab and then later showed.
[Fixed] - bug where the color levels feature in the imagetools dialog wasn't working properly.
[Fixed] - bug where imagetools dialog wouldn't pre-load images from CORS domains, before trying to prepare them for editing.
[Fixed] - bug where the tab key would move the caret to the next table cell if being pressed inside a list inside a table.
[Fixed] - bug where the cut/copy operations would loose parent context like the current format etc.
[Fixed] - bug with format preview not working on invalid elements excluded by valid_elements.
[Fixed] - bug where blocks would be merged in incorrect order on backspace/delete.
[Fixed] - bug where zero length text nodes would cause issues with the undo logic if there where iframes present.
[Fixed] - bug where the font size/family select lists would throw errors if the first node was a comment.
[Fixed] - bug with csp having to allow local script evaluation since it was used to detect global scope.
[Fixed] - bug where CSP required a relaxed option for javascript: URLs in unsupported legacy browsers.
[Fixed] - bug where a fake caret would be rendered for td with the contenteditable=false.
[Fixed] - bug where typing would be blocked on IE 11 when within a nested contenteditable=true/false structure.