Added monitor callback in NewtonSolver

- subclassable functor for callback
- is called between linear solve and line search
- u, delta_u and norms of both are passed to callback
Add a "make coverage" target for gcov/lcov output.

Thanks to Paul Bauman for figuring this all out.

Looks like we're only getting 30-40% coverage from "make check" at present.
Add getpot_parse utility for debugging purposes
Add GetPot Dollar-Bracket-Expression functions

Now you can use ${=funcname arg1 arg2} etc. for cmath functions
(except for pow and exp, already covered well enough by ^) and
cstdlib rand/srand functions.
Clean up gcov outputs during "make clean"
Clear the KDTree too!!!
discern whether we have been installed or not
link external-facing ExodusII files into include/libmesh
set back to executable
fix for no nanoflann
make building from a tarball work in the top-level
Override sorting locale in rebuild_libmesh_SOURCES

My locale wasn't doing POSIX sorting and the result was unnecessarily
large diffs when changing libmesh_SOURCES
Factor SyncNodalPositions out of that anonymous namespace so we can
use it elsewhere in the library.
Add a non-const getter for _mesh_sys
get_physics()/get_qoi() const/non-const getters
Better accessors for moving mesh problems
Fix moving mesh code parallelism, regressions
Allow spaces in matched square bracket tokens

GetPot was breaking "[tokens like this]" into "[tokens" "like"
"this]", which was fine for section names, but now in the near future
we can use square brackets for preprocessor-like directives too.
replace ibmesh_cast_ptr<> with dynamic_cast<> in FEMSystem::build_context ()
Adding netcdf.h rule to rebuild_makefile.sh