hambedded-image-aprs: add minimal aprs image

This image is an extension to core-image-minimal. It has aprs
utitilities (ax25-{tools,libs} and aprx daemon) to get the board working
with APRS easily.
hambedded-feed-configs: add feed config recipe

This package is for easily configuring opkg feeds in the image creation
process. The variables are controlled in distro.conf and feeds for
MACHINE_ARCH is added automatically.

This recipe is copied directly from meta-oe.
hambedded.conf: add distribution config

Add master distribution configuration for hambedded. Currently, it is
based on poky distribution and it adds a few configuration on top of it
to help hamradio users easily use the distribution. IPK is used as a
package manager, and at least 4 virtual terminals are specified.

For testing purposes, yocto 1.4.1 package feeds are used.