list datasets
show error messages on failed model update
add export format enum and allow export to output stream
Merge pull request #30 from martiner/model

show error messages on failed model update
Merge pull request #28 from martiner/report

add export format enum and allow export to output stream
Merge pull request #27 from martiner/datasets

list datasets
tweak grid elements

- rename AttributeInGrid to DisplayFormGridElement
- rename GridElement to MetricGridElement
- introduce common parent AbstractGridElement
- add typed constructors
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.getDefaultAttribute()
updated example