CallLog: Removes the artificial 500 call log limit

An average person makes ~5 calls per day, resulting to a call log going back only  about 3-4 months. This is simply too low in my opinion. There is no harm to keeping an unlimited call log, just like we have an unlimited SMS log.

Change-Id: If8d19cfc47cf1ee0141bc35caebeeb8a476d0bd0