Reconfiguration backend

1. in org.fortiss.af3.exploration
   • Introduce new ISynthesisCategory specialization in exploration.ecore
   • Consider in org.fortiss.af3.exploration.util.ExplorationCLIUtils.getExplorationTypeByArgument(String)
2. in org.fortiss.af3.reconfiguration
   • Introduce Z3ReconfigurationBackend (use Z3Backend as template)
   • Introduce ReconfigurationRun skeleton (use DeploymentRun as template
     # getSolutionEntryType(): returning AllocationEntry.class should be OK (redundant deployment)
     # getSolutionModelName() return e.g. “TA ->HW (redundant)”
     # All other abstract methods of SolverRun can be implemented as stubs for now
   • Integration of backend using org.eclipse.ui.startup extension point
     # Create specialization of IStartup
     # Register new backend in earlyStartup: IDSEBackendService.getInstance().registerDSEBackend(new Z3ReconfigurationBackend());
3. Include Backend settings defined in #4050 in this branch.

Test: Reconfiguration exploration is offered in “Synthesis” view of DSE perspective.

(from redmine: issue id 4063, created on 2020-09-23, closed on 2020-10-20)