Add Basic .appveyor.yml With Linux Build

The AppVeyor system does not work in my fork of the project.  To make
the build common between forks and the main, a .yml file should be used.

Outline the sections and basics in some comments as described in the
AppVeyor getting started notes.  Copy the build steps from the current
.travis.yml file.

Once the Linux builds are working, I can start guessing at how to get
the Windows one running as well.

.appveyor.yml

@@ -0,0 +1,53 @@
+# An AppVeyor build configuration file for the Barrier project
+
+
+##### General Configuiration #####
+version: '0.0.{build}'
+
+environment:
+  # these variables are common to all jobs
+#  common_var1: value1
+#  common_var2: value2
+
+image:
+  - Ubuntu
+
+platform:
+  - x86
+#  - Any CPU
+
+configuration:
+  - Debug
+#  - Release
+
+##### Setup Phase #####
+
+install:
+  - echo The Install has started...
+  - sh: echo ... for Linux
+  - cmd: echo ... for Windows
+  - sh sudo apt-get update && sudo apt-get install \
+      libxtst-dev
+      qtdeclarative5-dev
+      libavahi-compat-libdnssd-dev
+
+##### Build Phase #####
+
+# Use build_script for our Linux builds and build for .NET
+build_script:
+  - sh: ./clean_build.sh
+
+##### Test Phase #####
+
+# Use test_script for our Linux tests and test for .NET
+
+##### Deploy Phase #####
+
+##### Catching & Cleanup #####
+
+# Success
+
+# Failure
+
+# Finish
+