Change the way how runtime_into is handled, so it won't fail if remote server is down.

The URL which returns the runtime info started not to function after a
point, resulting with 400 - Bad request. The startup won't fail after
these changes. Removed the filter_modules capability, as I could not get
the filtered data displayed on the remote servers.
Add display_pid option in the config file.
When this value is present nodes belonging to the same group will be
rendered separately.
Add config option to configure send_to_viz interval
Change fieldnames in tcstate to follow erlang conventions
Added some specs and fixed some dialyzer warnings
Add some documentation
Add functions to obtain some metrics about the run state
Fix some dialyzer warnings related to the concurix vm.
Fix the previous change as erl_opts from the Makefile did not work
It was already used from the .config, so passing the erl_opts to
rebar compile did not work properly.
Reset the link counters after sending them out
Give back the reduction count in the duration
Add disable_posts option for debugging
Add some documentation and specs
Update README.md to reflect how to start cx_runtime