Reworking of lapack_shared_libs and similar properties (#1682)

* Turned <provider>_libs into an iterable

Modifications :
- added class LibraryList + unit tests
- added convenience functions `find_libraries` and `dedupe`
- modifed non Intel blas/lapack providers
- modified packages using blas_shared_libs and similar functions

* atlas : added pthread variant

* intel packages : added lapack_libs and blas_libs

* find_library_path : removed unused function

* PR review : fixed last issues

* LibraryList : added test on __add__ return type

* LibraryList : added __radd__ fixed unit tests

fix : failing unit tests due to missing `self`

* cp2k and dependecies : fixed blas-lapack related statements in package.py

var/spack/repos/builtin/packages/hpl/package.py

@@ -78,7 +78,7 @@ def configure(self, spec, arch):
             'MPlib        = -L{0}'.format(spec['mpi'].prefix.lib),
             # Linear Algebra library (BLAS or VSIPL)
             'LAinc        = {0}'.format(spec['blas'].prefix.include),
-            'LAlib        = {0}'.format(spec['blas'].blas_shared_lib),
+            'LAlib        = {0}'.format(spec['blas'].blas_libs.joined()),
             # F77 / C interface
             'F2CDEFS      = -DAdd_ -DF77_INTEGER=int -DStringSunStyle',
             # HPL includes / libraries / specifics