Updating Boundary Harmonics in Free Boundary

[lazersos]

It has been requested that an option exist to have the RBC/ZBS representation in the input files update in free boundary. Traditionally during free boundary optimization they are held fixed because they only serve as an initial guess. The proposal is to add a variable LBOUND_UPDATE which updates the input files as the code optimizes. However, we should note that this needs to be done after a minimum. For example if we calculate a minimum then in a given iteration the boundary harmonics should match those used for the calculation, not those from the wout. Also this information needs to be back-communicate to all processors. I would propose doing this by including a file called fbharm.ext which if it exists all files read before calling VMEC.

This enhancement was requested by @pomphrey and is spawned from the issue #60.

New variable: LBOUND_UPDATE
Behavoir: If set to .true. and lfreeb then write a while named fbharm.ext which has the previous minimums boundary haromincs. File written in call to stellopt_write_auxfiles.
Behavoir: If file fbharm.ext exists then update RBC,ZBS,ZBC,RBS in input namelist before calling VMEC. Can easily be added to stellopt_reinit_vmec