and add debug information to README, how to check all lua files

# Conflicts:
#	.gitlab-ci/build.sh

# Conflicts:
#	make-release.sh
#	release
#	site.mk

the value batman_adv.routing_algo must be set in site.conf now. It is not alowed to leave it empty any more

[skip ci]

# Conflicts:
#	README.md

- build only with -j 1 if VERBOSE is set
- add BUILD_LOG=1 to log in gluon/openwrt/logs and upload those folder too,
- compare empty string with -n
- also pipe errors into log

[skip ci]

reverted: batman: activate bridge loop avoidance (reverted from commit a9c312c21450ad8c1b6ec4797df57e069e210245)