add materialization scripts as examples

adopt spatial join

update sbt and plugins

Merge branch 'master' of dbgit.prakinf.tu-ilmenau.de:code/piglet

add visualizer command and add new STARK version and add new STARK version

allow to specify columns to perform difference on

add set methods INTERSECTION and DIFFERENCE

better code generation for spatial join + index

allow to sample any types, not just instances of SchemaClass

adapt spatial join for INDEXed data

INDEXed data can be written and loaded with MATERIALIZE op (and BinStorage)

encode indexed type with index class name

add support for INDEX operation to create spatial index that can be reused

add cogroup operator (for Spark)

fix config file setting for admission check