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/octopus/package.py

@@ -46,13 +46,13 @@ class Octopus(Package):
     # FEAST, Libfm, PFFT, ISF, PNFFT
 
     def install(self, spec, prefix):
+        lapack = spec['lapack'].lapack_libs
+        blas = spec['blas'].blas_libs
         args = []
         args.extend([
             '--prefix=%s' % prefix,
-            '--with-blas=%s' % to_link_flags(
-                spec['blas'].blas_shared_lib),
-            '--with-lapack=%s' % to_link_flags(
-                spec['lapack'].lapack_shared_lib),
+            '--with-blas=%s' % blas.ld_flags,
+            '--with-lapack=%s' % lapack.ld_flags,
             '--with-gsl-prefix=%s' % spec['gsl'].prefix,
             '--with-libxc-prefix=%s' % spec['libxc'].prefix,
             'CC=%s' % spec['mpi'].mpicc,