[gst] Support media.role in event configuration file

By default gst plugin use media.role=media.
When another media.role is needed it can be configured in event file in /usr/share/ngfd/events.d/

For example:
sound.stream.media.role = mymedia
Merge pull request #20 from tihonko/dev

[gst] Support media.role in event configuration file
Revert "mce: plugin follows and stores the display status"

This reverts commit c40e96058ddc3ea43e45f9536a81a2a03c1f9400.
Merge pull request #23 from kjokinie/master

[ffmemless] Add check for device existence to plugin loading
Merge pull request #22 from Vesuri/master

Revert "mce: plugin follows and stores the display status"
[ffmemless] Add missing function declaration

The ffmemless_erase_effect function declaration was missing
from the header file. Added so that the function can be used.

Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@jollamobile.com>
[ffmemless] Clear old effect before uploading new

If a effect with different type than an existing effect in kernel
is uploaded with same id, the effect loading fails. Solved this by
deleting the old effect before uploading new ones.

Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@jollamobile.com>