updated docs to better explain new features

the docs do not current reflect the new net-install and packages modules
changes well. This updates them to explain the new keys in the
configuration files.

src/modules/netinstall/README.md

@@ -37,6 +37,12 @@ More keys are supported:
       - subgroups: if present this follows the same structure as the top level
         of the YAML file, allowing there to be sub-groups of packages to an
         arbitary depth
+      - pre-install: an optional command to run within the new system before
+        the group's packages are installed. It will run before each package in
+        the group is installed.
+      - post-install: an optional command to run within the new system after
+        the group's packages are installed. It will run after each package in
+        the group is installed.
 
 If you set both *hidden* and *selected* for a group, you are basically creating a "default" group of packages
 which will always be installed in the user's system.

src/modules/packages/test.yaml

@@ -1,6 +1,10 @@
 rootMountPoint: /tmp/mount
 packageOperations:
   - install:
-    - vi
+    - pre-script: touch /tmp/foo
+      package: vi
+      post-script: rm /tmp/foo
+    - wget
   - remove:
     - vi
+    - wget