Bump version to 0.15.1; update CHANGELOG and version references

CHANGELOG.md

+# v0.15.1 (2020-07-10)
+
+This minor release includes several important fixes:
+
+* Fix shell support on Cray (#17386)
+* Fix use of externals installed with other Spack instances (#16954)
+* Fix gcc+binutils build (#9024)
+* Fixes for usage of intel-mpi (#17378 and #17382)
+* Fixes to Autotools config.guess detection (#17333 and #17356)
+* Update `spack install` message to prompt user when an environment is not
+  explicitly activated (#17454)
+
+This release also adds a mirror for all sources that are
+fetched in Spack (#17077). It is expected to be useful when the
+official website for a Spack package is unavailable.
+
 # v0.15.0 (2020-06-28)
 
 `v0.15.0` is a major feature release.

lib/spack/spack/__init__.py

@@ -5,7 +5,7 @@
 
 
 #: major, minor, patch version for Spack, in a tuple
-spack_version_info = (0, 15, 0)
+spack_version_info = (0, 15, 1)
 
 #: String containing Spack version joined with .'s
 spack_version = '.'.join(str(v) for v in spack_version_info)

lib/spack/spack/container/images.json

@@ -12,7 +12,8 @@
       "0.14.1": "0.14.1",
       "0.14.2": "0.14.2",
       "0.15": "0.15",
-      "0.15.0": "0.15.0"
+      "0.15.0": "0.15.0",
+      "0.15.1": "0.15.1"
     }
   },
   "ubuntu:16.04": {
@@ -28,7 +29,8 @@
       "0.14.1": "0.14.1",
       "0.14.2": "0.14.2",
       "0.15": "0.15",
-      "0.15.0": "0.15.0"
+      "0.15.0": "0.15.0",
+      "0.15.1": "0.15.1"
     }
   },
   "centos:7": {
@@ -44,7 +46,8 @@
       "0.14.1": "0.14.1",
       "0.14.2": "0.14.2",
       "0.15": "0.15",
-      "0.15.0": "0.15.0"
+      "0.15.0": "0.15.0",
+      "0.15.1": "0.15.1"
     }
   },
   "centos:6": {
@@ -60,7 +63,8 @@
       "0.14.1": "0.14.1",
       "0.14.2": "0.14.2",
       "0.15": "0.15",
-      "0.15.0": "0.15.0"
+      "0.15.0": "0.15.0",
+      "0.15.1": "0.15.1"
     }
   }
 }

lib/spack/spack/schema/container.py

@@ -32,7 +32,7 @@
                     'enum': [
                         'develop',
                         '0.14', '0.14.0', '0.14.1', '0.14.2',
-                        '0.15', '0.15.0',
+                        '0.15', '0.15.0', '0.15.1',
                     ]
                 }
             },