Clean unnecessary dirs from root home before doing snapshot
Coreginx helper isn't enabled by default anymore.
Added zshenv.served template.
Info header for do_binary_snapshot. It requires zsh.
Several changes and additions to install_script. More in details.

* stdout/stderr messages are logged into log file in /var/log
* install zshenv file
* explicitly call ignitersinstall on each installation
* cleaning bin archive after successful installation
* added checks for fetch/unarchive operations
Keeping zshenv in snapshot isn't necessary.