Salary for Absentees and New Players

I've updated the logic for allocating salary when a game is missed and for players added to the league part way through.

Absent: The player is given their average salary increase from all prior games. 

e.g. I missed game 4 so for this game I will be given my average increase based on games 1,2 and 3. 

New Player: The player is given their first salary increase multiplied by the week they entered plus the starting salary.

e.g. Graham Brown joined in week 6. He will receive his first salary increase * 6 + 500000 starting

Note that this only changed salary by more than 5% for 6 players in the league, 2 of which were new additions. There is some more analysis and code here if you are interested https://github.com/kevinhughes27/parity-server/pull/73