Update AppVeyor build configuration

* Update Windows build environment (Visual Studio 2017)
* Add build cache for local Maven repository

appveyor.yml

@@ -1,3 +1,19 @@
+version: '{build}'
+skip_tags: true
+clone_depth: 2
+branches:
+  except:
+    - gh-pages
+image: 'Visual Studio 2017'
+environment:
+  #JAVA_HOME: 'C:\Program Files\Java\jdk11'
+  JAVA_OPTS: '-Xms512m -Xmx2g'
+cache:
+- 'C:\Users\appveyor\.m2\repository'
+install:
+#- cmd: SET PATH=%JAVA_HOME%\bin;%PATH%
+- cmd: java -version
+build_script:
+- mvnw.cmd -V -B -ff install -Dmaven.test.skip=true -Dmaven.javadoc.skip=true -Dmaven.source.skip=true -Dmaven.deploy.skip=true
 test_script:
-  - mvn package
-build: off
+- mvnw.cmd -V -B -ff verify -Dmaven.javadoc.skip=true -Dmaven.source.skip=true -Dmaven.deploy.skip=true