Remove the @catch_exceptions handler.

Use .write_error() also in AWS and remove the obsolete
@catch_exceptions handler.
See commit c28273c7f9728fa4b092a7fc7958316d7a5d7827 for details.
TwoSteps: adapt for the TaskType refactoring

TaskType changed the internal API recently, but TwoSteps was not ported.
Merge pull request #24 from gcampax/two-steps-port

Two steps refactoring to follow the other task types
Fix a few long standing errors in RunTests.
Merge pull request #23 from gcampax/master

[REGRESSION] Various fixes to Batch tasks
OutputOnly: allow the comparator to get the input

The comparator may need to access the input file to find if a solution
is valid or not. The sandbox infrastructure was already there, but the file
was not fetched from the DB.
Allow HTTPS between SS and RWS

SS used to send username and password in plaintext in its requests to
RWS, allowing an eavesdropper to get them and send custom forged
requests to RWS. To fix this and to keep using HTTP Basic authentication
a transport layer encryption such as HTTPS is the ideal solution.

HTTPS is optional both in SS and in RWS. Plain HTTP communication can
still be used and username and password will still be sent in plaintext,
but this is intended mainly for cases where RWSs are used privately. For
public RWSs it's reccomended to use HTTPS.

When using HTTPS, SS will send username and password only if the HTTPS
certificate provided by RWS is trusted (it's checked using SS's own list
of trusted certificates). Thus, the communication will happen only if
both parties trust each other. This should prevent an eavesdropper to
obtain the username and password, even in case of a man-in-the-middle
attack.
Add more limits to the number and frequency of submissions and usertests

Allow to set a per-contest and per-task limit on the total number of
submissions and usertest sent by each user and on their frequency.

The per-contest limit applies to *all* submissions or usertests of the
entire contest, while the per-task limit applies only to submissions or
usertest for that task.

Note that the default per-task limit of a submission every 60 seconds is
no more. It can be added back using AWS.
Refactor Contest and Task Handlers in AWS

Use an uniform coding style among all of them.

Also, use multipart/form-data enctype since it's the only argument type
for which Tornado distinguishes between empty and missing arguments.
Fix links in the license notice in CWS

Make them open in a new browsing context.
AWS: Fix templates for output only submissions

OutputOnly submissions have a NULL language, so replacing %l unconditionally
raises an exception and a causes a critical error in aws.
Merge pull request #25 from gcampax/output-only

AWS: Fix templates for output only submissions
Fix escaping in announcements, messages and questions in AWS and CWS.

Fixes issue #22.
Fix bug on ALLOW_PARTIAL_SUBMISSION tasks

Has been introduced in f268441a413cb180ca11be1d7f05da6a561328b5
Fix the previous fix
Fix SS sending an escaped short_name for tasks

The escaping was intended only for the IDs of the entities, that have to
use the alphabet [A-Za-z0-9_]. This restriction doesn't apply to the
short_name field.
IOI and mailing list in README.md.
RunTests: don't check anymore for min_submission_interval.

It was removed from the configuration.
RunTests: rankings_address changed format.
Use 10 <col>s for first and last name (instead of 11) in RWS