dist fails if no launchConfig is porvided in .eosgi.dist.xml

[lgathy]

Based on the eosgi-dist.xsd this should be allowed, however a NullPointerException will be thrown at org.everit.osgi.dev.dist.util.configuration.DistributedEnvironmentConfigurationProvider lines 81 and 130 in org.everit.osgi.dev.dist.util artifact.
Proposed patch at: https://github.com/lgathy/eosgi-dist-util/tree/support-no-launchConfig
Also will send PR.