Transform data with any valid projection matrix

[eigenvivek]

Is your feature request related to a problem? Please describe.
Supersedes #417

Describe the solution you'd like
We're planning a bunch of new MORF experiments with different types of patches (convolutional filters, gabor filters, etc.)

Allowing the user to define and pass their own projection matrix sampling functions would make these experiments a lot easier, rather than having a new splitter class for every patch sampling method we want to try

I'm proposing modifying ObliqueSplitter's sample_proj_matrix to allow for user-defined matrix sampling methods.

Alternatively, i could make a new splitter class with this functionality

@levinwil @jdey4 @PSSF23 what do y'all think?

[PSSF23]

I personally think that modifying the existing function makes more sense, so it could save us an additional splitter class?