FETIDP: fix corner case

KSPFETIDP: implement Olof's idea on using BDDC for the pressure preconditioner

PCBDDC: fix propagation of use_qr_single if there aren't constraints

PCBDDC: remove the correct nullspace

PCBDDC: add getters for primal vertices

PCBDDC: fix improper usage of %d and \n in prints

add missing ierr = .. CHKERRQ(ierr); where needed

PCBDDC: added option to control target globalcoarse size

- use BDDC API after KSPSetFromOptions if the coarse pc type have been changed at command line
- minor indentation fixes

PCBDDC/KSPFETIDP: update XXXView ops

PCBDDC: propagate options prefixes to inner solver matrices

this is to namespace factor prefixes, e.g

-pc_bddc_dirichlet_mat_mumps_whatever_option

instead of

-mat_mumps_whatever_option

PCBDDC: propagate the correct error_if_failure flags to inner solves

PCBDDC: no need for the change of basis matrix to be AIJ

PCBDDC: Raise error if preallocation is not exact

PCBDDC: add events

PCBDDC: 8 additional levels is more than enough

It can always be changed by modifying bddc.h or with CFLAGS=-DPETSC_PCBDDC_MAXLEVELS=whatever

PCBDDCSubSchurs: add command line option to play with communicator

MATIS: speed up matrix assembly by using MatSetValues with large blocks

Merge branch 'barry/clarify-dmplex-documentation' [PR #917]

* barry/clarify-dmplex-documentation:
Rename DM[GS]etDefault{Global}Section() to DM[GS]et{Global}Section().
Add DMPlexComputeGeometryFEM()

MATIS/BDDC: handle a very strange case when MatISFixLocalEmpty gets called on a DMDA generated matrix with empty rows

MATIS: deprecate MatISGetMPIXAIJ in favour of MatConvert()

Updated code and tests

PCBDDC: use corners only if present (ptatin support)

PCBDDC: added command line option to filter small entries when detecting disconnected subdomains (damn dolfin)

PCBDDC: allow command line debug of SubSchurs

PCBDDC: use new API ISLocalToGlobalMappingGetNodeInfo

PCBDDC: added command line option to visualize the coarse matrix

Merge remote-tracking branch 'origin/maint'