update ChangeLog
update issue #157 try to find eigen3, added an option to try to find it or not (FEELPP_ENABLE_SYSTEM_EIGEN3)
update issue #157 remove various directories from release tarball
update issue #157 implement DVLOG_IF if not using contrib version
update issue #157 fix conflict between petsc and eigen : MatType is a c++
macro defined by Petsc and a typename defined by eigen
update issue #157 do not ship contrib libraries except for ginac
update issue #157 first try to find headers and libraries installed on the
system then use the contrib version
add support for Qt Creator
up changelog
Merge branch 'feature/contrib' into develop