Added an option to the OSEM estimator filters for PR3/SR3 that allows us to get v1 filters.

The v1 filters use the model at the first two L/P resonances of the SR3 and PR3 suspensions. [see images attached for an example of v2 vs v1]

The functions that construct these blends are the same ones posted in [LHO: 87613] and [LHO: 87596]:

blend_{PR3,SR3}_{length,pitch}v2_LP_est.m
The files must be run with the argument 'v1' to get the v1 filters out. For example, blend_PR3_lengthv2_LP_est('v1') will get the v1 filters for H1 PR3 in length.

If you run them with anything else (including no argument), they will get the v2 filters, same as before. However, I suggest running them as blend_PR3_lengthv2_LP_est('v2') in automated code so everything is clean for loading the filters into foton.

These changes have been committed to the SVN under revision 12745.