added 'round' column to PostsForAnswers to keep track of the

number of times the answer has been evaluated.

NOTE: database upgrade required
Currently one count is for each judgement, so if an evaluation has
two criteria, the answer will get two counts for each evaluation.
The main role of the new column is to attempt to ensure the
answes are evaluated a similar number of times. The ideal case
would of course be the same number of times for each answer.
refactored answer pairing algorithm

This is to keep the number of comparisons per answer evenly
distributed.
The answers are first grouped by the number of times they are judged.
Then we try to find the closest scored paris within the group
with the lowest number of comparisons. If a valid pair is not found,
we try to find a valid pair by merging the the next lowest number
of comparison group with the lowest number of comparison groups.
refactored new answer pairing algorithm

- the part I have fixed is:
	- not assume the lowest round only has one answer if no
	valid pair can be created.
		- will generate all possible pairs by pairing each
		answer in the lowest round with each answer in the
		second lowest round
	- if no valid pair can be found within the lowest round and
	after merging the lowest round with the second lowest round
		- we continue to try to match lowest round with the
		third lowest round
		- so on and so forth
	- if no valid pairs can be found at the end of trying to find
	a valid pair with the lowest round, we start again with the
	second lowest round.
- the tests have also been fixed.
changed the answer round increment mechanism

- the round counter increments by 1 for each evaluation instead
of 1 for each criteria.
Added CriteriaAndPostsForQuestions to AnswerPairing

- requires database upgrade
- existing answerpairs will be related to the first criteria of the
question
- This upgrade allows us the flexibility of possibly splitting the
evaluation form for each criterion so that it may be more fair
for the answer in all criteria.
fixed problems with inactive criteria being selected to be used

for comparing scores during the answer pairing algorithm