Now `graded_lc()` doesn't need a JGRADE column when `timecolor`==True.

This is super helpful for making colored lightcurves in Cygnus.
Now `graded_phase()` doesn't need a JGRADE column when `timecolor`!=False.
Added `period_decimal_places` to `graded_phase()` just like commit #46f6710.
Added `custom_xlabel` kwarg to `graded_lc()` just like in commit #387b71f