Support for multiple instances with different configurations

Introduces a command-line switch -c config-id or --configuration config-id.
This allows you to run multiple instances of swyh-rs where each configuration can use a different audio source.
Suggested by @cavadias, see issue #82.
Each configuration gets its own config file and log file in the .swyh-rs folder in your HOME directory, identified by the config-id (blank by default).
The delay when starting the webserver is removed as it can interfere with autoreconnect.

Windows binaries and setup, and Ubuntu 20.04 LTS and later (and Ubuntu derivates) appimage in assets.

Linux appimage for Ubuntu 20.04 and later.

Linux appimage in assets, built on Linux Mint 20. It will only run on Ubuntu 20.04 LTS and later systems I'm afraid, because GLIBC is not bundled by appimagetool. Built on Linux Mint 20, and tested on Linux Mint 20 (Ubuntu 20.04) and 21 (Ubuntu 22.04).

Fix for connection loss when pausing music with Sonos by @genekellyjr (issue #71)

• fix for pausing music with Sonos causing the Sonos to close the connection. This optionally injects silence at the music source, contributed by by @genekellyjr (see issue #71), with a new "InjectSilence" boolean flag in the config.toml (not exposed in the GUI). For this to work you have to
  • check that swyh-rs uses the same output as your music source in the Windows soundmixer
  • edit your config.toml and change the InjectSilence flag from false to true
• fltk-sys 1.3.14 builds again on Windows with MSVC, so we no longer need to use the fltk-bundled feature

Windows release and debug binaries, and setup in assets.

Linux release binary in assets (compiled on Ubuntu 22.04.1 LTS).
A universal Linux musl binary is currently not possible because the alsa-sys crate does not support static linking.

Fix for multiple identical soundcards

• handle duplicate sound card names by storing the index too (solves issue #70)
• make the CaptureTimeout for LPCM/WAV configurable in the config.toml, with a default of 2000 msec (as it was hardcoded before). If no sound is captured for a CaptureTimeout period, a block of slience of (CaptureTimeout / 4) msec length is sent to the receiver (was previously 250 msec hardcoded). See also issue #71.
• for some reason I can no longer compile fltk on Windows with MSVC, so fltk-bundled is used for now on Windows

Windows 64 bit binaries and setup in assets

FLAC streams: Don't send anything if no sound captured

The player may abort the streaming, depending on it's FLAC implementation.

Windows 64 bit binaries and setup in assets.

remove unneeded OGG support from libflac-sys build

flac-bound now allows building libflac-sys without OGG.

Windows 64 bit binaries and setup, linux Ubuntu 20.04 binary in assets.

Small UI change for FLAC

From now on no more 32 bit support, because I can't get libflac-sys to build for 32 bit.

Windows 64 bit binaries and setup, and Linux Mint binary (Ubuntu 20.04) in assets.

Flac support (16 and 24 bit)

First release with FLAC support.

64 bit Windows binaries (release and debug) and setup in assets.

Fix possible vulnerabilities caused by outdated dependencies in the ifcfg crate

Remove possible exposure to security vulnerabilities CVE-2021-45707 and CVE-2022-24713 by replacing the use of the ifcfg crate by the if_addrs crate.
This removes the dependency on outdated and vulnerable versions of nix and regex in ifcfg.

Windows 64 bit and 32 bit binaries and 64 bit setup in assets.

Fix broken AV Transport (again)

Fixes issue #59

Windows binaries (64 bit and 32 bit, release and debug) and setup in assets.