install: create dotfiles directory

Refer #54
init: moved codeblock to create dotfiles
init: generate ssh keys for redmine user

Refer #54
install: move supervisord process to /var/log/redmine/supervisor/

Refer #52
install: move nginx process logs to /var/log/redmine/nginx

Refer #52
install: do not create `/home/redmine/data` in the install script