Finalize retuning of LRG cuts for DR9 and modify LRG SV bits

[geordie666]

This PR supersedes #660. It includes code to:

• Retune the LRG cuts for DR9 and update the LRG SV target bits.
• Switch to only using the default BRIGHT, GALAXY and CLUSTER masks in MASKBITS (i.e. ignoring ALLMASK and MEDIUM).
• Increase the SV faint limits from z < 20.5 to z < 21.0 and from zfiber < 21.9 to zfiber < 22.0.

[geordie666]

@rongpu: I incorporated your work from PR #660 into this branch. A bunch of function calls needed to be modified to account for your new inputs to the isLRG() function and I figured it would be most expedient to make those changes myself. I believe that unit tests should now pass on this branch. But, could you quickly check that I didn't actually change any of your intended cuts?

If you think this looks good, I'll merge it once unit tests pass.

[rongpu]

@geordie666 I checked these changes and they look good. Thanks!