use build tool version 20
refs #190 no arrayindexoutofbounds
refs #173 show vertical and/or horizontal grid lines or no grid lines
refs #83 warning if static labels and setNum...Labels are used together
refs #130 no more Log.d
refs #191 multiline labels (line break support)
refs #153 maven push properties
compatible to aapi version 7
graphview 3.1.3