cleanup refine_mesh code in core.cc

Avoid initializing unused vectors, cleaner SolutionTransfer code,
formatting.
report convergence failures in release mode

A recent change causes the linear solvers to hang in release mode (with
more than one process) if we don't reach convergence.
Merge pull request #129 from tjhei/fix_solver_errors

report convergence failures in release mode
Merge pull request #128 from tjhei/core_cc_formatting

cleanup refine_mesh code in core.cc
Writing &(variable) always strikes me as wrong because things in parentheses
are expressions, and taking the address of an expression should yield, at
best, a lambda function. I know that's pedantic but I know I'm a pedant and
the patch makes me happy!
Merge pull request #130 from bangerth/expressions-are-not-variables

Writing &(variable) always strikes me as wrong because things in parenth...