rewrote adaptive view stuff so we can use it on all types of views
(model-based, multi timestep, multi-mesh)

- separate setNode and tagNode in API

- ported Gradient, Curl, Divergence, Integrate and Transform plugins
  to the new abstract post-pro API

- documented new post format

change new post API to allow multiple meshes in a single view (different
meshes in different steps)

- temp fix I/O to allow skipping $xx fields (this will be common
  with new post-pro)
- prune MElement (move mesh-only stuff in mesh algos)

airplane work: more work to complete remaing features (read, combineSpace,
combineTime) in new post-pro

- re-add smooth() for PViewDataList

- removed static GMODEL (can now have multiple models)
- added infrastructure for new post-processor module