Add next generation default environment template ...

This adds a new environment template which aims to be more flexible
and configurable. Instead of having mainly two scripts (a config script
and a boot script) this template uses initscripts which control the
startup behaviour and configuration. Also we have boot scripts in
/env/boot which configure a single boot configuration. Additional
boot entries can be added by board specific entries or during runtime
by copying and editing a template entry.

Some more helpers handle for example network interfaces which can now
be brought up with 'ifup'. We use the automount feature to configure
mountpoints together with the commands to bring up the devices behind
these mountpoints.

Optionally menu support is available which hides many details behind
a nice looking interface.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>