Add systemd specs and following remarks:

* In RPM/DEB we introduce new utility - tarantool_ctl (extra/dist/dist.lua)
* /var/pid -> /var/run
* Fix extra/dist/dist.lua
* /extra/dist/tarantool.init and /extra/dist/tarantool.service now
  are regenerated by cmake (paths to `dist.lua`)
* Systemd service (Uses sysv-init script)
* RPM Supports both systemd and init (by using '--with systemd' in
  rpmbuild flags)
Small fixes
Merge remote-tracking branch 'origin/rpm-systemd'