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.

devuan/resources/config.sh

@@ -0,0 +1,18 @@
+
+# FusionPBX Settings
+system_username=admin           # default username admin
+system_password=random          # random or as a pre-set value
+system_branch=stable            # master, stable
+
+# FreeSWITCH Settings
+switch_branch=stable            # master, stable
+switch_source=false             # true or false
+switch_package=true             # true or false
+
+# Database Settings
+database_password=random        # random or as a pre-set value
+database_repo=system            # PostgresSQL official, system, 2ndquadrant
+database_backup=false           # true or false
+
+# General Settings
+php_version=7                   # PHP version 5 or 7