Add support for (django) internalization

Run cactus makemessages first. (See the README in the locale folder).

Rolled back the changes to discover the cactus site path so as to not to
break existing applications by complaining that locale does not exist.
Merge branch 'i18n'
Add support for variables in the config file
Added support for multiple config files
Add support in the CLI for multi config
Add support for re-definition of `variables`

This lets users define multiple (context) variables in different config
files.
Merge branch 'multi-config'