IB: use online repositories

Change the IB packaging to only embed libc, kernel and kmod packages by default
and generate repositories.conf to refer to the remote package repositories.

Introduce a new config option CONFIG_IB_STANDALONE which restores the old
behaviour of building self contained IB archives.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@45772 3c298f89-4303-0410-b956-a3cf2f4a3e73

[imagebuilder] populate repositories.conf from version.mk

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@31268 3c298f89-4303-0410-b956-a3cf2f4a3e73

[imagebuilder]
- sync with host opkg changes
- get rid of autogenerated opkg.conf
- utilize dl/ as package cache, useful for remote downloads


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@23039 3c298f89-4303-0410-b956-a3cf2f4a3e73

[imagebuilder]
- add a helper script to generate opkg.conf, attempt to detect package architecture from packages/
- fix package defaults when no package override is given, IB previously aggregated the defautls of all profiles
- introduce a repositories.conf, allows using remote opkg repositories in imagebuilder


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@22978 3c298f89-4303-0410-b956-a3cf2f4a3e73