Add getSimByPhoneNumber(String) method to the SimService.
Finish work-around for accounts with multiple SIMs (relevant tickets: #37 and #67).

* When computing pricing points for incoming CDR's, assume all SIMs have the same call connectivity type, and use the CCT of the first SIM in the account.
* When constructing an invoice, look up the right SIM by its telephone number to find the data bundle associated with this data use.