Fixed correlation example, fixes to error messages
Merge pull request #157 from kosovan/master

Fixed correlation example, fixes to error messages
Removed last traces of ignore_charges
Now also checking O3 if O5 is not possible (e.g. llvm)
particle print no longer checks for runtime errors, which cannot occur anyways
Removed the dysfunctional invalidate_system, updated checkpointing documentation.
Removed invalidate_system voodoo from tests
Updated NEWS.
Clarified docs on checkpointing.
Updated autotools files.
Missing cells_tcl.hpp
Merge branch 'master' of github.com:espressomd/espresso
ScaFaCoS compilation.
Add derived features to code_info.
Merge branch 'master' into scafacos

Conflicts:
	src/communication.cpp
Make p3m_wall testcase generic for electrostatic methods.
Small additions