Added tutorial for grav2d and put Makefile.am back in
gravity example output directory (there are two .pvsm files in there).
Cleanup gravity example directory.

Remove output directory (move ParaView state files to main directory).
Small cleanup of Makfiles in configure.ac.
Updated README to reflect change in directory structure.
Simplify script to generate spatialdb file with initial stresses.
Decrease file size of figure images.

Reduce jpg quality to 85% to reduce file size.
Small cleanup of figure display and formatting.
Merge branch 'willic3/add-examples-grav2d'

* willic3/add-examples-grav2d:
  Small cleanup of figure display and formatting.
  Decrease file size of figure images.
  Simplify script to generate spatialdb file with initial stresses.
  Updated README to reflect change in directory structure.
  Small cleanup of Makfiles in configure.ac.
  Cleanup gravity example directory.
  Added tutorial for grav2d and put Makefile.am back in gravity example output directory (there are two .pvsm files in there).