define acceptable system dependencies for mfext and add an integration test to enforce them

[x] introduce linux_distributions_dependencies_checker to check some system libraries in various linux distribution
[x] define a first list of acceptable system dependencies (checked by the previous tool) : here
[x] introduce a non-blocking integration test for centos6 builds (only)
[x] fix problem with libffi.so.5 (some work done in #441)
[x] fix problem with libreadline.so.6
[x] fix problem with libgfortran.so.3 : first move libnetcdff from scientific_core@mfext to scientific@mfext in mfextaddon_scientific and then we should be able to remove libgfortran (and libgfortran4) for .system_dependencies in scientific_core@mfext
[x] fix problem with libtcl8.5.so
[x] fix problem with libtk8.5.so
[x] fix problem with libpng12.so.0
[x] check the integration test which should be ok
[x] uncomment exit 1 line in integration test (blocking mode)
[x] remove (system) tcl/tk, linpng, libffi, libreadline from build images and system dependencies
[ ] push similar integration test for all modules and addons (from resources repository), blocking for mfext, non-blocking for others
[ ] open issues on corresponding repositories where we can find some problems

metwork-framework / mfext