Add ids to problems

[ss0201]

required for #153. #96 is also solved by this, I think.

[exKAZUu]

Does ids mean unique numbers (0, 1, ....) regardless of contests?
E.g. the ids of the first problem and the second problem in a same contest may be 1030 and 1032.

[exKAZUu]

Mongo DB gives ids to any records, I think. Can we use them?

[exKAZUu]

Please make clear how to specify ids for problems.

[ss0201]

Here IDs are specified by the problem author, which are currently included in the problem titles. I think adding IDs to problem solved #153 and #96.

[exKAZUu]

Hmm. I have an idea.
Add a new string field named "id" whose default value is id (integer) of Mongo DB multiplied by 10.
Sort problems by the ids and show alphabets (A, B, C .. ) instead of actual "id" value.

e.g. Problem1, 2 and 3 has 240, 250 and 260 ids, respectively. An admin changes the id of the problem 3 to 245. Then, users see the A, C and B ids of problem 1, 2 and 3 instead of 240, 250 and 245, respectively.

[ss0201]

lol, that's like line numbers in BASIC :) That is better than my first suggestion, but I have another idea: let the admin order problems with a drag-and-drop UI (just like http://jqueryui.com/sortable/), and show alphabets in this order.

[exKAZUu]

Okay, okay, we will implement the best way to order problems.
But I think this issue is quite large. We want more time to implement it.