enable ddt support for memory debugging
off by default, need to switch it on in Debug build type
clear big objects in Doftable
clear big object in FunctionSpace
created test directory for leaks 
moved test_solve_leak to feelleaks
copy
clear
added leaks
remove virtual
force cleanup
cleanup
find ddt and its dmalloc library for memory debugging
@vhuber fix compilation (thx cdash)
@vhuber I missed one
test only in sequential
 @doyeux @vhuber fixed execution using loadMesh() and simplify the code. Updated .cfg
merge