SLICE-39 Add new method to ModelProvider
Merge branch 'master' into SLICE-39

Conflicts:
	slice-core-api/src/main/java/com/cognifide/slice/api/provider/ModelProvider.java
	slice-core/src/main/java/com/cognifide/slice/core/internal/provider/SliceModelProvider.java
	slice-core/src/test/java/com/cognifide/slice/core/MockModelProvider.java
SLICE-39 NPE prevention + doc updated
Merge pull request #34 from Cognifide/SLICE-39

SLICE-39 Add new method to ModelProvider