feat(engine): add correlation method in runtime service

- adds correlation of executions by process instances variables
and business key
- adds correlation to message start events

contributes to CAM-664
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
style(example): Improve labels in invoice process model
improve(example): Set isDeleteUponUndeploy to false
feat(engine): add correlation handler to engine configuration

- added to ProcessEngineConfigurationImpl

closes CAM-665
feat(welcome-site): add favicon to welcome page
fix(engine): fix ExecutionQuery#processInstanceBusinessKey

- now selects all executions that belong to a process instance with a
given business key

closes CAM-111
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
chore(engine): refactor execution query in DefaultCorrelationHandler

contributes to CAM-664
Merge pull request #4 from falko/invoice-beautification

Improve invoice showcase
fix,feat(ProcessApplication): embedd and config

- BUGFIX: fix problem with embedded process application deployment: "default job
  executor not found". Embedded process application configured through
  processes.xml now uses DefaultjobExecutor provided by
  ProcessEngineConfigurationImpl. <job-acquisition> field in processes.xml
  file is now optional. In order to use container job executor in embedded
  deployments, corresponding MBean must be deployed manually.

- FEATURE: in order to test fix, feature for providing custom
  processes.xml file location is added by commit:

  @ProcessApplication(deploymentDescriptors={"my/location/processes.xml"})

related to #CAM-659, #CAM-678
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
feat(spring): add support for spring process apps

- add SpringProcessApplication and SpringServletProcessApplication for
  supporting process application bootstrapping using spring.
  #CAM-446

- add support for defining a managed process engine inside a spring
  process application context xml file. The process enigne bean must be
  constructed using the new
  org.camunda.bpm.engine.spring.container.ManagedProcessEngineFactoryBean
  #CAM-445

- add support for Spring Expression Resolving in process applications
  through
  org.camunda.bpm.engine.spring.application.SpringProcessApplicationElResolver
  #CAM-444
chore(it): revert arquillian config
chore(spring): fix maven dependency scope
fix(welcome-site): use screenshots with camunda logo and cleanup css code
fix(glassfish) Glassfish requires no internet connection to start

replace all deprecated sun-web.xml in Glassfish WARs with glassfish-web.xml

related to CAM-667
Merge remote-tracking branch 'refs/remotes/origin/master'
fix(engine): make correlation handler initiation overridable
Merge pull request #5 from camunda/spring

feat(spring): add support for spring process apps

* add SpringProcessApplication and SpringServletProcessApplication for
supporting process application bootstrapping using spring.
#CAM-446
* add support for defining a managed process engine inside a spring
process application context xml file. The process enigne bean must be
constructed using the new
org.camunda.bpm.engine.spring.container.ManagedProcessEngineFactoryBean
#CAM-445
* add support for Spring Expression Resolving in process applications
through
org.camunda.bpm.engine.spring.application.SpringProcessApplicationElResolver
#CAM-444