remove dependencies

close: #15
Merge pull request #44 from martiner/dep

remove dependencies
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