installation script for OS Devuan (#95)

* adding devuan

* add devaun desc to README
make update and upgrade more noisy
correct path for devuan in pre-install

* some untested code for the source install - source installation is broken in Debian installation script and I have not debugged the problem. Focusing on the packaged version first.

README.md

@@ -12,6 +12,15 @@ It supports the latest video dependencies. If you want to do video mixing use De
 wget -O - https://raw.githubusercontent.com/fusionpbx/fusionpbx-install.sh/master/debian/pre-install.sh | sh
 cd /usr/src/fusionpbx-install.sh/debian && ./install.sh
 ```
+### Devuan
+If you like Debian but rather not bother with systemd, Devuan is a "drop in" replacement.
+Version 1 is bassed on Jessie. So you will find the same packages available.
+Please note that the source installation and installation on ARM is not fully tested.
+
+```sh
+wget -O - https://raw.githubusercontent.com/fusionpbx/fusionpbx-install.sh/master/devuan/pre-install.sh | sh
+cd /usr/src/fusionpbx-install.sh/devuan && ./install.sh
+```
 
 ### FreeBSD
 FreeBSD is an operating system that has many great features like ZFS, HAST, CARP and more.