Initial changes to AppVeyor to also build code with VS 2017

Author: solodon4

appveyor.yml

@@ -37,12 +37,20 @@ environment:
   BOOST_ROOT: C:\Libraries\boost_1_59_0
   BOOST_LIBRARYDIR: C:\Libraries\boost_1_59_0\lib64-msvc-14.0
   matrix:
+    - toolset: 2017
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
     - toolset: 2015
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
     - toolset: 2013
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
     - toolset: 2012
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
     - toolset: 2010
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
 #   - toolset: 2008 - not really supported by Mach7. Just here as a reminder worker supports it
+#     APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
     - toolset: analyze
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
 #   - toolset: cmake -G "MinGW Makefiles" - still configuration errors. Ignoring for now
 #   - toolset: make - make is not available via PATH variable