developers/index.html: remove "Experimental build systems"

The benefits of the CMake build system are now provided by GNU Make,
which is now the default.  Configure gives instructions for using
builder.py.
website: minor clean-up in developers and mailing list pages
Mat: Added MatGetLayouts() which allows for access to row and column layouts.
PCGAMG: Remove use of matrix-internal scatter context from Direct interpolation
PCGAMG: Remove scatter use for indices from Standard interpolation
PCGAMG: More cleanup after the switch
Insure that all ASCII viewers for PETSc objects call PetscObjectPrintClassNamePrefixType()
do not require -fopenmp to compile streams
webclient code requires PETSC_USE_SOCKET_VIEWER
Merge branch 'knepley/fix-plex-gmsh'

* knepley/fix-plex-gmsh:
  DMPlex: Fixed bad declaration style
DMPlex:Fix compiler warnings
Merge branch 'knepley/fix-plex-gmsh' into next

* knepley/fix-plex-gmsh:
  DMPlex:Fix compiler warnings
Merge branch 'knepley/fix-plex-gmsh'

* knepley/fix-plex-gmsh:
  DMPlex:Fix compiler warnings
changes to examples due to objects always printing class and name information
added  MPI_MAX_PROCESSOR_NAME for MPIUni
fixed streams/process.py script to work cleanly with NPMAX=1
Merge branch 'master' into next
DMPlex: Fix up HDF5 segregation
REVERT TS: Timestep gets set into DMTS
DM: Add idea of an output sequence
- Added DMGet/SetOutputSequenceNumber()
- Added doc for outputDM
DMPlex: Handle output sequences
- Added static to some functions
TS: Set output sequence for timesteps