Introduce inital draft of hawkBit SDK (#1638)

Intends to provide a Java SDK facilitating:
* development of back-end integrations using mgmt api (including UI-s)
* development of java based high-end devices (which could run Spring apps) to communicate with hawkBit via DDI API
* implementation of demo/test cases using device & management SDK

Status: initial draft
 - Feign client did & management API - done
 - Hal/HATEAOS Support - works (including in non-web apps)
 - device communication works when no software updates (e.g. pulling software base)
 - demo for single and multiple devices simulation (including management API uses)
 - TODO - fix software update flows
 - TODO - provide more integration points for developers to interact with device SDK

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

hawkbit-rest/hawkbit-mgmt-resource/src/main/java/org/eclipse/hawkbit/mgmt/rest/resource/MgmtTenantManagementMapper.java

@@ -46,4 +46,4 @@ public final class MgmtTenantManagementMapper {
             .withSelfRel().expand());
         return restConfValue;
     }
-}
+}