Add a timer when checking solutions

[ngsankha]

Currently there is no timer implemented in the Codejudge Compiler Server Java code. Thus the eval.php file will not return if somebody submits a program that takes very long to complete or infinite time to complete.

Thus a timer needs to implemented, that will run the program for a specified maximum time only. If the program takes more than that it will be terminated and the user will be shown an appropriate message. Things required to implement it are:

• Maximum time that will be allowed for each problem should be specified in the Problems page, ie. problems.php.
• Appropriately update the Codejudge Compiler Server's Java code.
• Define error signals in the Java source if the program terminates prematurely and accordingly update eval.php.
• Store the time taken by each solution in database so that it can be used in the calculation of scores.

[ngsankha]

Closed by commits from f14c6722a1 to cb54f79929.