work on #301: define product of space easily
cleanup doc,see #300
re-organize the document and try to make it more coherent, see #300
rework the tutorial and make it a step-by-step tutorial, see #300
Merge branch 'feature/productspaces' into feature/doc
improve integrals tutorial, see #300
allow printing expressions using c++ i/o  streams
Update #300
 - Improved documentation and tutorial
 - Improved support for symbolic calculus : added grad, div, laplacian for scalar
   and vectorial functions
 - Added support for list of expressions
use Eigen::Map and Eigen3 in updateJKBN()
no need for isomorphism
up
Update #00:
 - improve menu (removed QSCompile. reorganize,...)
 - minor modifications
cleanup :)
update #300
 - cleanup FAQ
 - moved how to doxygen doc in FAQ
define evaluate_type for Expr::evaluate() function
Update #238 use Eigen3 for Geomap::updateJKBN()
factorize Ginac classes and symbol handling
they now support the same interface symbol-wise
update #301 work on product of function spaces
Merge branch 'develop' of https://github.com/feelpp/feelpp into feature/doc

Conflicts:
	feel/feeldiscr/functionspace.hpp
fix cmake