add no null elements array validation
add utility method for translating md obj array to uri array
add report public constructor with report definition vararg
change method name returning a single result to getObjUri
refactor Obj as interface
add getObj() method returning Obj instance by restrictions
add: Attribute.getDefaultDisplayForm()
update readme
Merge pull request #33 from martiner/rep

Add MetadataService.getObj() method returning Obj instance by restrictions