Fixed button formating on MarkingCode
Undid some previous work on account modification

I realised that users are supposed to be able to have duplicate accounts
for different roles, so I undid some of the work I did previously the other
day (deleting or changing type of instructors/TAs). The text fields for
instructor ID and the TA list on the create course page are now uneditable,
and there will have to be a "Delete TA" button on the create course page
so that no invalid data can be entered in the database. This is because
I had to remove the foreign key constraints on the tables (InstructorID
and Name no longer reference accounts, same for TA table) so that we could
have multiple accounts for one person.
Merge pull request #246 from firethanatos/master

Design doc modifications
Moved submit button to left for rubrics
Click the big logo on the login page

- You'll see.
Field checks in create course
Fixed fugly top_panel - #247
MarkingCode now displays files (kind of)
Fixed create course page
Added Shell IO classes

- Got from:
  http://alvinalexander.com/java/java-exec-processbuilder-process-1
Fixed #248
Shell calls can be made via Shell.exec - closes #232

- There is also a method to make python calls directly.
Fixed broken compiling
Removed Logger.java
Removed unused imports
Added `lines` function
Added diffutils library
uneditable test suite
MarkingPDF UI Updates

Prepared for Markus' PDF magic
Fixed editable text fields