improve(rest test): extend expected exception responses

contributes to CAM-730
fix(license): Add license header to classes
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
 Prepare release: set version to 7.0.0-alpha4
 Next development version: 7.0.0-SNAPSHOT
fix(select-dataType): Fix datatype selection

- fix datatype selection in tasklist
- by changing the data type the process will not be started anymore

related to CAM-702
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
improve(javadoc): PA classes
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
feat(rest): improve exception mapping

- adds RestExceptionHandler that translates exceptions explicitly
thrown in the REST API to responses with specific error codes
and a json message body that includes the exceptions type
and a detailed message

contributes to CAM-731
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
fix(tasklist): fix group task counts

closes CAM-741
improve(rest): rephrase exception messages for queries

CAM-694
fix(rest): improve resteasy test runtime performance

- exchanges twjs server by netty
- greatly improves test runtime

closes CAM-431
chore(rest): cache loggers
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
feat(rest): add DELETE process instance

contributes to CAM-641