250 add latex upload download pdf feature

[DJWalker42]

PDF output from Latex justification text can now be obtained from the front end GUI.

• Split the Justifications modal into three tabs. The 'Editor', the 'Latex Service', and user 'Help' tabs.
• The text format selection immediately updates the Justification
• The text itself still has to be saved by manually by pressing a button
• The cancel button now has "unsaved changes" protection, and user cannot click outside the modal to close (the 'x' still closes the modal regardless)
• 'Latex Service' has a "compile" button, with a text-area underneath to display the results of the compilation
• As with SupportingDocuments, the PDF download is done in two steps, "request" then "download".
• the 'Latex Service' also provides upload functionality for users to add, list, and remove their resource files (.bib, .png, .jpg)