wallet treats transferred coins as "immature"

Dooglus, 

I believe this should fix the issue we were seeing with coins being immature when they shoudn't be. 

AvailableCoinsMinConf now only checks the 510 blocks when its a coinstake transactions, all other transactions will become available after 10 confirmations + the 4 hours of course. 

Checking for IsCoinBase() should not be required as all the POW blocks that were created are 30k+ blocks deep at this point.

Reopened from issue #13