feature: number station over web radio (icecast+liquidsoap)

[hiryu85]

Fixes #11

Requirements

• icecast server
• liquidsoap python library

Tasks

• [x] radio beahavior: play single or a set of songs (playlist) [with liquidsoap]
• [x] numbers station message: encryption
• [x] numbers station message: encryption with random key (--key-rand)
• [x] numbers station message: message over on current playing song
• [x] numbers station message: message amplified [with liquidsoap]
• [x] support multiple stream: each stream have a custom config, and behavior (change main.liq is required to change default behavior)
• [x] helper: create playlist from music/ directory files
• [x] helper: clone default stream with another name and replace all paths in configs
• [ ] testing
• [ ] doc about new features

[DonaldTsang]

Happy new year, buddy. This is really promising I can tell you that. It seems that Azuracast is making a move to include RaspberryPi support to make things more convenient. But don't let that get you down, a lot can be done to make this a lightweight alternative.

A review on features:

1. Audio playlist that has everything in "normal mode"
2. Fading in and out of message on certain times of the day or week
3. Message based on a designed spelling alphabet
4. (bonus) message encryption by any form or means
5. (bonus) usage of external m3us for extra playlist flexibility