Add 'create_inventory_context' command

The command 'create_inventory_context' can be used to dump all the
nodes from reclass inventory, they names from recalss.storage,
and any additional keys from nodes if needed, for example:

$ reclass-create-inventory-context \
    -d mcp11-ovs-dpdk.local \
    parameters.linux.network.interface \
    parameters.linux.storage
diff --git a/setup.cfg b/setup.cfg
index 10aad7b..985cf66 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -31,3 +31,4 @@
     reclass-show-key = reclass_tools.cli:show_key
     reclass-inventory-list = reclass_tools.cli:inventory_list
     reclass-vcp-list = reclass_tools.cli:vcp_list
+    reclass-create-inventory-context = reclass_tools.cli:create_inventory_context