Add support for MM charges and positions.

[adam-grofe]

To support QM/MM, we need a method to report the positions and charges of the MM atoms. Here, we add an extension to the xyz file parser to add an optional postscript to provide this data. For the MM charges and positions, we use the same format as the xyz file itself but with an additional column for the charges of the MM atoms. e.g.

3
water
O   0.00   0.00   0.00  
H   1.00   0.00   0.00  
H  -1.00   1.00   1.00  
--MM--
3
MM water
O   0.00   0.00   2.00  -0.6  
H   1.00   0.00   2.00   0.3  
H  -1.00   1.00   3.00   0.3 

Where there is one QM water molecule and one MM water molecule.

[adam-grofe]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).