Add splits for K2SC de-trending as as attribute

[ekaterinailin]

What needs to be created or improved?

We need a list of split indices as attribute in FlareLightCurve. This is then fed directly to detrend(). append() needs a feature that will add another split index = len(first_FLC)

What is the goal / expected behaviour?

We have a dict of default splits that talks to FlareLightCurve.__init__(). Appending FlareLightCurve objects introduces one additional split value and updates the indices of the appended object with += len(FlareLightCurve.flux).

[ekaterinailin]

I do no longer support append, and splits can be passed to FlareLightCurve.find_gaps() now. I did not implement a splits attribute to FlareLightCurve.