Change software_config storage of config and io columns

Previously the config column was of type LongText and all config
scripts were expected to be strings. However there will be many
config formats which are best stored and returned as parsed data
structures (tripleo metadata, cfn-init, ansible, salt).

This change converts the software_config config column to Json
and deletes the io column. The config, inputs, outputs and options
are now stored in the config Json column as top-level dict entries.

No data conversion is needed for this migration since nobody is
using software-config in the wild yet.

partial blueprint hot-software-config-rest

Change-Id: I03dc528bc2a6b255d6baa0eb8b9c1c8a7e6f872c
Merge "Change software_config storage of config and io columns"