Use shape finder when it's not provided

[dcangulo]

I have a lot of the following code when it can be included internally instead:

direction, curve = find_shape(x, y)
kl = KneeLocator(x, y, curve=curve, direction=direction)

PS: this may be a breaking change on some projects since I'm changing the default values and they depend on the default concave and increasing without setting it explicitly and it don't match with what find_shape returns.

or we can keep concave and increasing as the default and just add another bool parameter like use_shape_finder, where if it's True then find_shape will be used so that it will not be breaking. Let me know what you think. Thanks!