goodbye make
Build variants, install target, etc.

--HG--
rename : SConstruct => SConscript
Install the causal header too
Readme updates
Install coz-plot and coz-process
Tool name, plus install targets for processing and plotting

--HG--
rename : tools/causal/SConscript => tools/coz/SConscript
rename : tools/causal/causal.cpp => tools/coz/coz.cpp
coz is no longer built with baked-in path to libcausal.so