Option for start RVs

[mzechmeister]

The option should accept an RV file.
Currently, there are already the -vtfix and -skippre options. Actually, it is also related to the -targrv option.

With is option one could, for example, apply RVs from CARM_VIS for the coadding in CARM_NIR.

[mzechmeister]

Currently, start RVs could be loaded by writing them into the *.pre.dat file and using the -skippre option.
This is how vtfix works since 73e1fd8:

serval/src/serval.py

Lines 1059 to 1066 in 73e1fd8

	if vtfix:
	# RV are zero
	np.savetxt(prefile, np.array([(sp.bjd, 0., 0.) for sp in spoklist]))
	if skippre or vtfix:
	# restore the pre RVs
	if os.path.isfile(prefile):
	bjd, RV, e_RV = np.genfromtxt(prefile, dtype=None, unpack=True)