generate FEELPP_ENABLE_RESEARCH_<PROJECT> option which is OFF by default
and can be turned on when the user wants to develop/compile/use a research project
Merge branch 'develop' of https://github.com/feelpp/feelpp into develop
 - automatic list projects in research whenever a README.md file exists in a
subdirectory of research
 - add option FEELPP_ENABLE_<PROJECT> which is set to OFF by default. when set
 to ON then the project will be compiled alongside feel++
improve feelpp add application
 - add NO_SEQ_TEST to disable sequential tests
Merge branch 'develop' of https://github.com/feelpp/feelpp into develop