Support for jingle saving

[denis-stepanov]

Currently the process of jingle fingerprinting is completely detached from regular AdVent use. One has to separately record a stream, search for jingles, cut out and fingerprint. This feature would allow while recognizing to save some snapshots around a user-indicated hit, facilitating later fingerprinting and submission to the database. This feature builds up on another things to implement:

1. Dejavu modification to save input into files;
2. Support for interactive controls #8