repo: use all mirrors/baseurls when downloading a package.

dep: this is only allowed by the 0fbe1c3 commit in librepo.

Related: RhBug:997658
logging: nicer logging during transaction.

Fix the capitals, add a line about the trans check succeeding.
logging: start and stop of the actual RPM transaction.
comps: adapt to changes in libcomps handling of env.group_ids.
Adapt to librepo-1.0.0, handle.url is handle.urls now.
New version: 0.4.0
build: 0.4.0-1