Added comment on required invocation order

To use vtkUnstructuredGrid's InsertNextCell, you must have called its
Allocate method.  This was documented on Allocate, but not on
InsertNextCell.  Someone with a segfault in InsertNextCell will not
be looking at the documentation for Allocate.  This change adds a line
to the documentation of each overload of InsertNextCell to inform that
Allocate must be called first.

Change-Id: Idacf2081ded84a27fc574e85904e9082ff5c8536
BUG: Writing an Exodus file in parallel segfaults.

This happens when data is only on a node.

Change-Id: Id03fb63e46593f2e9ca24180c6091dace64df7f5
Stop all processes if one process stops.

If running in parallel and saving multiple time steps, if one
process stops executing all processes stop.

Change-Id: I1fee5599a1acaad230235db421961f602a3e342e
Merge topic 'fix-docs-on-call-order-dependency' into master

a8d27882 Added comment on required invocation order
BUG: Fixed error in passing position of key press

Thanks to Maarten Beek for pointing this out on the VTK users list.

Change-Id: Ic964ff5bb3b8c69560ff7c80a1a0eee976ff5be3
Merge topic 'context-interactor-key-bug' into master

9a918305 BUG: Fixed error in passing position of key press
Merge topic '14539-can-crash' into master

b45e6b63 Stop all processes if one process stops.
699deb91 BUG: Writing an Exodus file in parallel segfaults.