Flag/tag based refinement additions

[shivankhullar]

Pulled in flag based refinement changes from my older C version. Tested these changes out, seems to be working fine for me with this C++ version. Summary of additions:

1. Makefile changes to rusty, timestep.cc had a syntax error on line 735, increased InitCondFile and OutputDir memory allocations to 200 characters.
2. Added FLAG_BASED_REFINEMENT flags to do the flag based refinement (explained in Template_Config.sh). Essentially these flags will read in a field called "RefinementFlag" from the IC file and then use those tags to calculate a center for the refinement region. Allows one to tag particles of any type in principle and use their COM as the RefinementRegionCenter. To generate ICs for these, simply add another field called RefinementFlag and add a header attribute called RefinementRegionCenter (which can be initialized to zero since we calculate this on initialization anyway).
3. FLAG_BASED_REFINEMENT_MAXDENSITY will lock-in the refinement region center on the maximum density (replacing the COM calculation). Useful for choosing one region among many collapsing centers in a large 0.5 kpc cloud.
4. JEANS_REFINEMENT_IN_REGION and JEANS_REFINEMENT_IN_REGION_RADIUS_PC should be used with FIRE_SUPERLAGRANGIAN_JEANS_REFINEMENT to define a region within which refinement is allowed. JEANS_REFINEMENT_IN_REGION_RADIUS_PC sets the outer radius of the region. The inner radius (at highest res, beyond which there's no splitting), is set to JEANS_REFINEMENT_IN_REGION_RADIUS_PC/20 for now, but can be modified as needed. There's a condition to choose the maximum of this m(r) function and the target resolution based on the FIRE_SUPERLAGRANGIAN_JEANS_REFINEMENT criteria, so we have a spatial gradient in resolution that's set automatically as gas collapses.