try to detect init-system and install accordingly

typo #82, improvement #81

Check if systemd log2ram service is running before the install;

better for flexible shell

typo for #32

Suggestion from #46

The last bracket shall not be glued to the directory.

The actual code is generating a runtime error like the following :
 erwan@raspberrypi:~/download/log2ram $ sudo ./install.sh
 Created symlink /etc/systemd/system/sysinit.target.wants/log2ram.service → /etc/systemd/system/log2ram.service.
 ./install.sh: 19: [: missing ]
 ##### Reboot to activate log2ram #####

This patch simply adds the missing space to make this script work.

The init is useless and the mount was async.

Log on disk wasn't copy on install, so the shutdown destroy everything.
#18 #17

It's maybe the pb of #17

- Since the cron job could be called before the user reboots after
  install (or if log2ram is disabled), we check that the hdd log
  location exists before syncing.

- Copy the log2ram.hourly sync script to cron's hourly directory on
  install.

no x flag for logr2ram.server