More eigen.m4 flexibility

Check more environment variables when figuring out where to look for
Eigen headers

Allow configure.ac (in other programs) to search for Eigen/Dense
without failing if a working Eigen/Sparse is missing.  This should
probably be given a better mechanism...
Define another testable variable, HAVE_EIGEN
fix cut & paste bug that caused constraining DOFs to be multiply added.
initial infrastructure for user-specified element refinement selection
implement roys suggestions
Merge pull request #55 from benkirk/user_spec_refinement

initial infrastructure for user-specified element refinement selection
must always make flags parallel consistent, even for serial meshes, if the user is allowed to do direct flagging
forgot to AC_SUBST a var
Minimum version number test option for eigen.m4
Document and assert DoF/DofObject proc id identity
Patch based on Manav Bhatia's type-mixing methods
Patch from Manav Bhatia: gmsh format 2.2 support
Manav's proposed "fix" for UnsteadySolver AMR
Patch from Manav Bhatia: templated read datatypes
Default template parameters to avoid API breakage
Adding standard type implementations for MPI blocking send/receive
Correct fix for UnsteadySolver::reinit()

Looks like Manav identified a real bug which just hadn't been hit by
the particular way my own AMR/transient loops interleaved.  His
original fix could have introduced a new problem in other corner
cases, but this reduced fix seems to handle the bug triggered by his
app but shouldn't add any new bugs in others' apps.
Merge pull request #60 from permcody/parallel_fixes

Adding standard type implementations for MPI blocking send/receive
Merge pull request #61 from roystgnr/manav_unsteady

Manav's and my fix for an UnsteadySolver+AMR failure
Warn about inconsistent flags

As discussed regarding c5298f15f73136dc3291de1e56541aacce6eb779,
redundant refinement flag synchronization might be expensive, but
allowing inconsistent parallel refinement flags to break a large code
that could have been fixed by redundant synchronization might be
offensive.  This patch aborts upon finding inconsistency when in
debug/devel modes, but simply fixes the problem, warns about it, and
continues when in opt mode; this way we can fix any such bugs and
users should be safe to remove the redundant synchronization later.