pom.xml modifications for reproducible builds

Seems to produce fat JARs with the same MD5 after repeated runs of:
mvn clean package

Needs testing on other platforms, hence this commit.

Also trimmed some unneeded included JAR libraries from pom.xml,
e.g. netty, async-http-client,
and the *.js.map files from Swagger-UI, which seems to reduce
output JAR size from about 51MB to about 44MB.

src/main/resources/build.properties

@@ -1,2 +1,2 @@
-build.timestamp=${build.timestamp}
-build.version=${project.version}
+build.timestamp=${git.commit.time}
+build.version=${project.version}-${git.commit.id.abbrev}