Remove dependency on Media module

Problem/Motivation

The BrandfolderStreamWrapper extends the MediaReadOnlyStreamWrapper class provided by the Media module. This is sensible in itself, but Media is a large module, and it would be better not to force Brandfolder users to install it.

Steps to reproduce

Enable the Brandfolder module. Note that the Media module must also be enabled.

Proposed resolution

Reimplement the necessary methods in the BrandfolderStreamWrapper class so that it implements the DrupalStreamWrapperInterface interface by itself.

Remaining tasks

Code and test.

User interface changes

None.

API changes

None.

Data model changes

None.