log: default logging to timestamped files

Log messages to timestamped files as default,
avoiding to overwrite existing ones.

The default location of the logs was changed,
to improve /var/log/ovirt-engine sanity.

/var/log/ovirt-engine -> /var/log/ovirt-engine/ovirt-log-collector

A log rotation was introduced in order to compress old logs.

Bug-Url: https://bugzilla.redhat.com/1009116
Change-Id: If180bb3c425d94449236147cddc17c504bf602b7
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>