chore(REST): add docs how to deliver a message to multiple executions

related to #CAM-2006
updt(user.guide): add postgres 9.3 to supp env
updt(user.guide): add link to supp env of 7.1
fix(deployment descriptors): proofread and correct

related to #CAM-2423
fix(BPMN files): proofread and correct

related to #CAM-2406
chore(rest): unify 204 media type
fix(rest): fix return codes
chore(rest): adjust response example
chore(ProcInstQuery): extends docs about REST API

related to CAM-2371
fix(REST): proofread and correct

related to #CAM-2189 #CAM-2190 #CAM-2191 #CAM-2192 #CAM-2194 #CAM-2195
 #CAM-2196
chore(deployment-descriptors): add additional resource suffixes docs

- rename process element of process archive (processes.xml) to
  resource
- add property additionalResourceSuffixes to process archive
  (processes.xml)

related to #CAM-2383
fix(userguide): Amend PA Overview section

related to #CAM-2440
fix(deployment-descriptors): proofread and correct

related to #CAM-2383
feat(user-guide): add camunda:script as execution listener

related to #CAM-2360
feat(rest): form variables

- document form variables for tasks and process definitions

related to #CAM-2436
chore(guides): migrate getting started guides

related to #CAM-2285
chore(user guide): add filter examples

related to #CAM-2121
fix(user guide): fix links to roundtrip with other BPMN 2.0 Modelers

related to #CAM-2477
feat(user-guide): add camunda:script as task listener

related to #CAM-2361
fix(links): changed links for supported version

related to #CAM-2474