Adds RCSID login functionality and a new proof saving method

Users must authenticate to start using LEGUP. This will be a problem if
non-RPI students wish to use it.

Proofs are now saved using binary data serializations of the board
state.
Adds submission functionality

Multipart file upload via POST
Adds security features and server compatibility bugfixes
Adds icon for directions button
In addition to the merge, changed Login's constructor to not prompt for
login on startup.

Merge branch 'authentication'

Conflicts:
	code/edu/rpi/phil/legup/BoardState.java
	code/edu/rpi/phil/legup/CaseRule.java
	code/edu/rpi/phil/legup/saveable/SaveableProof.java