Improve data access via virtual satellite headless

[franzTobiasDLR]

In this PR, we imrpove the generall usage and data access of our Virtual Satellite Headless Server.

Includes

• Enable customization of Port (and prints activated port)
• Return new objects instead of only their UUID on POST requests
• Improves error response if user does not have rights to modify data model (as specified in the Rolemanagement)

[codecov]

Codecov Report

Merging #1175 (176fbab) into development (8027909) will decrease coverage by 0.11%.
The diff coverage is 64.51%.

Additional details and impacted files

@@                Coverage Diff                @@
##             development    #1175      +/-   ##
=================================================
- Coverage          86.90%   86.79%   -0.11%     
+ Complexity          5147     5145       -2     
=================================================
  Files                629      629              
  Lines              25659    25681      +22     
  Branches            2331     2333       +2     
=================================================
- Hits               22298    22290       -8     
- Misses              2578     2606      +28     
- Partials             783      785       +2     

Files	Coverage Δ
...dlr/sc/virsat/server/resources/ApiErrorHelper.java	90.00% <100.00%> (ø)
...c/virsat/server/resources/ModelAccessResource.java	82.69% <100.00%> (ø)
...ources/modelaccess/CategoryAssignmentResource.java	81.81% <100.00%> (-7.66%)	⬇️
...modelaccess/StructuralElementInstanceResource.java	78.94% <100.00%> (-9.29%)	⬇️
.../dlr/sc/virsat/server/VirSatServerApplication.java	0.00% <0.00%> (ø)
.../dlr/sc/virsat/server/jetty/VirSatJettyServer.java	81.57% <27.27%> (-9.47%)	⬇️

... and 2 files with indirect coverage changes