small changes in order of things after a time step

the new order is now
 - timestep successfully finished
 - update episode
 - serialize to disk
 - print end of time step message

The old order was:
 - timestep successfully finished
 - print end of time step message
 - serialize to disk
 - update episode
fix quite a few warnings that occur on clang when using -Weverything

most warnings were in DUNE and ALUGrid, but these have been
ignored. Also fixing some of these warnings (in particular the
"parameter foo is unused" ones) would make the code harder to read and
understand, so they have been ignored, too...
Always use the reduction of the maximum of the weighted residual as convergence criterion

This should make things a much more robust, partially because now the
linear and the non-linear solvers use the same convergence criterion.

Also, this patch includes some collateral indentation improvements.
add method to query the world size to the domestic overlap
use the domestic overlap's peerSet() method
parallel iterative solvers: doc update, add missing solvers and precoditioners
domestic overlap: add possibility to map indices to something else

this is quite useful for debugging this shit...
feed the correct residuals to the newton method's updateError()
add a test for the parallel AMG linear solver

so far, it was only tested in sequential mode...
linear solvers: allow them to converge before the first iteration

i.e., allow linear solvers to become a no-op. This is required for
some convergence criteria.
fixup! Always use the reduction of the maximum of the weighted residual as convergence criterion
clean up the DGF grid files a bit
FvBaseNewtonMethod: fix writing of convergence files, renames
fix jacobian recylcing and output something if it was applied
remove the remnants of line search

and some other minor changes. (if you need line search the issue is
probably caused a different problem and line search would be just a
work-around anyway.)
add a few assertations to catch bugs more quickly
fix the generic globalResidual() method of the discretizations
use the correct communication interface for the ghost syncronization
Added required dependencies on opm-parser and CJSON
Removed explicit cJSON dependency from opm-core