This allows altering the LICENCE text without changing all files. It should
avoid merge conflicts in the future.

Api updated : Error spotted by D Barbier fixed alongside another one, and add a definition of scalfmm_call_delete()

Adding a scalfmm_execute_only_far_field method to the API, in order for a user to compute a FMM without P2P

Empty CMakeLists added to BenchEfficiency repertory in order to be able to compile FMMApi, CKernelApi and/or others addons

Changes in API, new call back for M2M and L2L where we provide the array of cells instead of calling the M2M over each child

hmat: fix installation of hmat addon (headers are copied in includes/ScalFmm/HMat/Src/.../*.hpp or includes/ScalFmm/HMat/CClusteringLibrary/*.h); Still need to fix pb when including cluster.h.

HMat: Provided data files (single precision) for mds (biology) in order to test clustering; Provided test routine and class for k-means clustering (actually k-medoid, since more robust and uses only distance matrix); Connected components can now be performed on a distance matrix read from file.

HMat: Provide new geometry, new distance and Gaussian covariance (+ associated matrix kernel); Resulting matrix has low rank off diagonal blocks (can be checked using testCompareClusteringRank).