Remove Cray examples of config files

Removed examples of Cray config files and added them under Spack on
Cray. Any users of Cray can just look at the Spack on Cray section to
get an idea of what's used. If they want more information they can click
links to the sections.

lib/spack/docs/configuration.rst

@@ -81,17 +81,6 @@ If Spack is asked to build a package that uses one of these MPIs as a
 dependency, it will use the the pre-installed OpenMPI in
 the given directory. Packages.yaml can also be used to specify modules
 
-Here's an example of an external configuration for cray modules:
-
-.. code-block:: yaml
-  packages:
-      mpich:
-        modules:
-            mpich@7.3.1%gcc@5.2.0 arch=cray_xc-haswell-CNL10: cray-mpich
-            mpich@7.3.1%intel@16.0.0.109 arch=cray_xc-haswell-CNL10: cray-mpich
-
-
-
 Each ``packages.yaml`` begins with a ``packages:`` token, followed
 by a list of package names.  To specify externals, add a ``paths`` or ``modules``
 token under the package name, which lists externals in a
@@ -195,35 +184,6 @@ concretization rules.  A provider lists a value that packages may
 ``depend_on`` (e.g, mpi) and a list of rules for fulfilling that
 dependency.
 
-For Cray users, you can specify the default compiler that Spack will
-concretize too. If you want to use the Cray defaults, then set them
-under all: in packages.yaml. You can also specify concretization preferences
-to cray-mpich. Just set the cray-mpich external module as a preferred package,
-set buildable to False and set the preference of mpi to mpich.
-
-Here is an example of a full packages.yaml used at NERSC
-
-.. code-block:: sh
-   packages:
-    mpich:
-        modules:
-            mpich@7.3.1%gcc@5.2.0 arch=cray_xc-CNL10-ivybridge: cray-mpich
-            mpich@7.3.1%intel@16.0.0.109 arch=cray_xc-SuSE11-ivybridge: cray-mpich
-        buildable: False
-    netcdf:
-        modules:
-            netcdf@4.3.3.1%gcc@5.2.0 arch=cray_xc-CNL10-ivybridge: cray-netcdf
-            netcdf@4.3.3.1%intel@16.0.0.109 arch=cray_xc-CNL10-ivybridge: cray-netcdf
-        buildable: False
-    hdf5:
-        paths:
-            hdf5@1.8.14%gcc@5.2.0 arch=cray_xc-CNL10-ivybridge: cray-hdf5
-            hdf5@1.8.14%intel@16.0.0.109 arch=cray_xc-CNL10-ivybridge: cray-hdf5
-        buildable: False
-    all:
-        compiler: [gcc@5.2.0, intel@16.0.0.109]
-        providers:
-            mpi: [mpich, openmpi, intelmpi]ackages:
 
 Profiling
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