Currently there are local coordinate systems that are stored in the global session component MyCoordinateSystem.

This seems to only really be used so when building a new grid near an existing grid the alignment snaps to the other grid. It should be possible to do this by just querying the pruning structure for nearby grids and snapping the build placer to those grids.

The local coordinate system code is also used when connecting grids together using GridSmallToLargeComponent. This should probably just be done by comparing the orientation and position of the two grids directly.

Reasons to remove:

• all coordinate systems appear to be persisted on the session
• there's some bug where fractured grids take over the coordinate system's orientation and cause it to move around, making future builds snap to a weird orientation