Allow default installation on modules

[mackensen]

We're contemplating using this block with the Poster module. Right now that requires a tedious workaround:

1. Add a poster module to a course
2. Add the Quickmail block
3. In the block configuration, change the value of "where this block appears" to "any page".
4. Navigate to the poster; the block will appear on the page.
5. Change the configuration again, from "any page" to "Poster module main page".

If mod is added as a supported applicable format we can add the block directly to the poster in the first instance.