Better use of coordinate systems

Coordinate systems aren't used very consistently.  For example, adding a second 
coordinate system and then adding a cylinder causes the new cylinder to be 
added at the origin and relative to the new coordinate system.  But performing 
a transform operation, the global CS is used.

I think, for consistency, when a coordinate system is active, all operations 
should be executed relative to that system.  This would include 2D operations 
like revolving a sketch.

Also, the relationship between objects and coordinate systems should more 
apparent.  Two possibilities:

1) Objects always exist in the global CS.  Stored coordinates are global 
coordinates.  Transforms are performed relative to the active CS but converted 
to global coordinates.

2) Objects have a relationship to a CS.  Stored coordinates are local.  
Changing the coordinates of a CS would also change all of the related objects.  
It should be possible to move objects into and out of a CS.  The relationship 
should be obvious from the tree.

Original issue reported on code.google.com by shopinth...@gmail.com on 16 Dec 2010 at 3:40

t0mac0 / heekscad

Better use of coordinate systems #325