Improved Docker build and docker images (#1488)

* Using upacked Spring layers for faster boot
* Added option to pass JAVA_OPT to modify the environment variables in both flavours
* Build support for different hawkbit apps - could be used in future if hawkBit is split in multiple micro-services
* Removed templates and replacing with parameterized (via build ARGs) docker builds

Signed-off-by: Marinov Avgustin <Avgustin.Marinov@bosch.com>

check-dependencies.sh

@@ -21,4 +21,4 @@ fi
 
 mvn clean install -DskipTests -Ddash.skip=false \
   --projects '!org.eclipse.hawkbit:hawkbit-repository-test,!org.eclipse.hawkbit:hawkbit-dmf-rabbitmq-test' \
-  -Ddash.summary=${DASH_SUMMARY}  ${DASH_IP_LAB}
+  -Ddash.summary=${DASH_SUMMARY} ${DASH_IP_LAB}