PCBDDC: extend coordinate based corner detection to the multilevel case

PCBDDC: fix area computation in corners selection

PCGAMG: do not raise the error, simply free the data

PCIS: allow specify the scaling vector in subdomain ordering

DM: Eliminate DMPlexGet/SetAdjacencyUseCone/Closure() in favor of DMGet/SetBasicAdjacency()

PCBDDC: simplify and improve nullspace correction code

- nullspace propagated only once
- correction done in KSP pre/post solve
- memory efficient: only dense basis stored

PCML: fix possible segfault when the ml_object is missing

PCBDDC: use Amat or Pmat in static change

PCIS: use exact interior matrix if requested

Patch: Fix memory leak, and test output for extra info in -view

Some C90 fixes

Fix more bugs when y is locked in VecScatter(x,y)

Do not do scatter to the same vector simultaneously

More logically collective remarks

Some documentation, variable declaration alignment, spacing

Revert "Undo/understand before merge: revert 95dbaa6faf01fdfd99114b7c9e5668e4b2aa754d"

This reverts commit 96372cdac3ae0e7b6f0dae2d347ffa16ffbd862a.

Some fixes to precomputation of tensors for facets. Working now.

Merge branch 'master' into wence/feature-patch-all-at-once

PATCH: WIP Plausibly implement precomputation for interior facets

PATCH: Fix indexing when inserting into matrix

Now all at once assembly works

PATCH: Assemble all element tensors once

PCTelescope: Group translate rank
* Since I do not want to check the error, code, I cast the function to void to shut of the static analyser (good tip from BarryFSmith)

PCTelescope: Removed duplicate call

PCTelescope: Code formatting and name spacing
* Aligned variable declarations
* Removed unnecessary blank lines
* Name spaced private function isActiveRank()
* Use PETSC_STATIC_INLINE for the privat

PCTelescope: Code formatting and name spacing
* Aligned variable declarations
* Removed unnecessary blank lines
* Name spaced private function isActiveRank()
* Use PETSC_STATIC_INLINE for the private functions PCTelescope_isActiveRank() and PetscSubcomm_isActiveRank()

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Telescope: Bug fix
* Fixed doc typo
* Fixed memory leak occurring on successive calls to PCSetUp.