rename flag to --disable_external_sources
use main repo in Dockerfile
remove obsolete dependency from Dockerfile
improve Dockerfile
Merge branch 'master' of obelix.fnrd.net:paulbox/fnordmetric

Conflicts:
	Dockerfile
add Run via Docker instructions to documentation
don't use PRIu64 since some compilers seem to not like it
use MYSQL_CLIENT_LIBS
Merge commit '6cf2d84aa74ce193e3935847f8ff099f006337a6'