[Aggregator] add rename feed possibility (fix #311)
[Aggregator] Slightly refactored channel deserializing.
[Aggregator] Added Channel{,Short}::DisplayTitle for #311.

This also includes the SQL backends.

Sorry for the huge commit.
[Aggregator] Show display title if not empty for #311.
Merge branch 'feature_311' of https://github.com/Maledictus/leechcraft into issue_311
[Aggregator] Suggest old name on channel renaming for #311.
[Aggregator] Operate on DisplayTitle on renaming.

This finally closes #311.
Merge branch 'master' of github.com:0xd34df00d/leechcraft