fix for hdiv/hcurl projection (#251, #252, #254)
 - mathematical formulation 
 - udpate Scalar/Vectorial cases
ignore
add test_hdiv (#251)
 - check basis function on ref/real element 
 - check projection (hdiv) on ref element
Merge branch 'develop' of https://github.com/feelpp/feelpp into develop

# Please enter a commit message to explain why this merge is necessary,
# especially if it merges an updated upstream into a topic branch.
#
# Lines starting with '#' will be ignored, and an empty message aborts
# the commit.