Combine individual and composite mask loops #93

The functions for composite masks and individual LPT system masks share a lot of the same code, and repeat much of the same computations. Therefore, it should be more efficient to combine them into one function that calculates both composite and individual masks. The idea is, as the individual masks are being calculated, the loop should keep track and update the composite mask. Then, at the end, it can write out the composite mask, instead of having to go through the entire calculation again.

This might use a bit more memory, but not much, since only one individual mask is stored in memory at a time, and the big array for composite masks is needed anyway.

Also, if composite mask and composite MJO mask are both turned on, it could easily keep track of which MJO LPTs are MJO, and update an array for MJO LPT composite mask.

I think it can work, and it would greatly simplify the process of running LPT code.