File attachment support

[F43nd1r]

Resolve #558
Resolve #561

[F43nd1r]

@MFlisar I've updated the project with a builtin content provider for all standard directories. So you'd only need a custom ContentProvider for non-file content.

[MFlisar]

I'll check that tomorrow. Only thing to take care of is, I would not use this provider. It's unsafe, other apps could access all files that the app which is using ACRA can access.

I think, the default one in acra should only allow to access files in a cache folder, for safety reasons even only for files in a sub acra folder...

[F43nd1r]

The content provider is not exported. Only apps called by ACRA will receive temporary permissions for exactly the files in the intent.

[MFlisar]

Oh, then it's fine. I've not seen that...

[F43nd1r]

Android takes care of the security management. That is the only reason to use content uris over file uris in this usecase.