Align panel as a package

I have decided to move the grid align panel into a separate package as well. There are a number of reasons for removing it from the core package:

• The panel is not useful as a dependency for other scripts

• It adds menu clutter to Unity for people who do not need it

• I don't expect that many people to have use for it compared to the core

• Installing a Git package is trivial

None of these points are particularly strong, but I cannot think of any downsides, so the decision was an easy one to make. In return I have added a sample to the package: a playground scene with some grids and objects you can move around and experiment with the different options. Such a sample would be pointless in the core, but it is appropriate for an external package.