feat: ipcamera support

[kstasik]

I needed this crate to setup some home automation and got tired of homebridge. Few things changed:

• ifaddr had to be updated
• basic tlv support had to be added
• i made pointer aliases public because they are used by public traits anyway - i didn't want to copy them
• basic camera support added

In case of ipcamera I have created trait which can be implemented for ffmpeg if needed.

I decided to use gstreamer bindings. It worked well with my hikvision ip camera. IMO the code is not perfect but better than nothing.

gstreamer18 support is needed to build it for raspberrypi (glib dependency).