minimize packagelists for 8MB-devices

[Martin Hübner]

After the 1.2.0-release we got feedback, that 8MB-devices ran out of flash memory and thus weren't able to store changes anymore. We should reduce the packageset to meet that needs.

1. Fast solution would be, to remove some packets from the package-list. Unfortunately this would reduce the pre-installed functions. I'd propose to start with tools like tmux, etc. Users that need those tools could easily reinstall them via opkg.
2. We could implement the function that we spoke of several times: The buildsystem could use a reduced packagelist for the 8MB devices. Thus we remain the useful tools on most devices.

Are there any further suggestions?

@pmelange @spolack @PolynomialDivision

[pmelange]

I think this issue should be moved to the builter repo.

[Martin Hübner]

with #96 we removed batman and dependencies, which could save around 174 kiB. That should hopefully be nough space to store some configuration modifications.