Wraps "repel" and "magnetized" mods into a base class

[o-dasher]

This pull request aims to address code repetition between OsuModRepel and OsuModMagnetized mods by creating a base class CursorBasedHitObjectPositionMod (This naming seens odd but i couldn't think of anything else) which both mods inherit from.

[bdach]

This was not done originally very intentionally. I didn't think that code reuse in this particular case worked well.

This PR is a little better in that respect, but there is so little shared code, that I question if this is even worth it.

[peppy]

It may make more sense if this is being done as a prerequisite to a new mod which is being worked on – is that the case?

[o-dasher]

It may make more sense if this is being done as a prerequisite to a new mod which is being worked on – is that the case?

That's not the case, i just figured out that this could be simplified and did it for the sake of code quality and ease of use

[peppy]

I think in the interest of simplicity, let's keep these separate for now. If there's ever a third mod of the same variety, it may be time to consider combining some code, although i'm not sure inheritance is the correct path.