Improvements and additions related to tps
- Fix factor of 2 bug in TpsCost
- Upgrade TpsCost to handles withe different weights and regularizers for each coordinate
- Move the matrix precomputations to inside TpsCost, except for the nullspace matrix N (since the caller needs that)
- Add the standard closed-form tps_fit3 and tps rpm cpp implementation as well as python wrappers for them