Kore applications now get a build.conf which may contain different
build flavors. Each flavor can get its own cflags or ldflags.
This was in parts inspired by #106.
A new cli command has been added:
kore flavor
This command allows you to see all flavors and switch between them.
The kore build command now also takes a -v argument which if given
dumps the used CFLAGS and LDFLAGS out to stdout.
For existing applications the build.conf is automatically generated
next time you run kore build or kore run.
Also fixed a bug in the json_yajl example, sneaky change here.
Allows one to bind a callback to a Kore task which is called
everytime activity happens on the task channel.
Add an example as well on how this works.
Inspired by issue #68.
