start a radio tx thread to centralize transmit requests
update defconfig

fix all apps to init the system before using devices.
We still have a problem: when sysdaemon is used as startup, and we run additional apps, the radio device FDs are not valid anymore. we need to fix this by sending radio packets to the sysdaemon with a thread and work queue.

Move all build defconfigs to their own folder
Update main readme according to new folder structure