PLAT-502 Add body field to downloadables

[Saphyel]

Fixes https://jira.comicrelief.com/browse/PLAT-502

[pvhee]

@Saphyel I'd like you to include a behat test on this as well or adapt the current tests on downloadables we have to include that.

[pvhee]

This probably needs to include also the search api config to make sure that field is indexed, if not yet the case? or adapt the search index view mode for downloadables.

Can we include that to the search tests as well?

[Saphyel]

@pvhee what do you wanna test exactly?
So at the moment is only searching for "Display title" but if we want to be able to search the body too we must update the default view (and use a different one where we don't want to show the body)

[Saphyel]

PhantomJS has crashed :)

[bimsonz]

@Saphyel is this the PR where travis is failing? its related to the test that is failing... that makes me think you must have changed something...?

[Saphyel]

@bimsonz I added new view modes (for solr) and a new field (optional) but all of this is out of tests...