Fix for NPE when cube message does not have number of stations for magnitude
Removed clone of BigInteger
Removed redundancy from before cube fields were BigIntegers
Safer null handling in QuakemlToCube conversion, and allow messages without magnitudes to convert
Updated CubeToQuakeml to better support messages without magnitude
Fix for logic error, when magnitude is not null but magnitude error is
Merge pull request #4 from jmfee-usgs/npe_num_mag_stations

Fix for NPE when cube message does not have number of stations for magni...