Gapless playback / eliminate silence while connecting to stream

[exquo]

Feature request: after clicking on a play button for a station, do not turn off whatever audio is already playing on the phone (be it another station in RadioDroid, some music from a music app, or anything else) while the app attempts to connect to a radio stream.

Currently, after clicking on a play button, the currently playing audio is immediately stopped, and there are a few seconds of (uneasy :) silence until RadioDroid starts to get data from a stream. Also, a connection to a stream might fail altogether if the internet connection is flaky, or if a streaming server is down; this takes up precious time that could have been spent productively listening to something else :)

Related issue: #994.

P.S. Thanks for all you work on radio-browser.info and this app!