refactor(engine/test): fix test naming

related to #CAM-2028
chore(test/multipleEvent): Add testcase for multiple start event

- the testcase try to test the behavior of the bpmn parser for
multiple start event
- the bpmn parser doesn't support multiple start events

related to #CAM-2029
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
fix(variable/concurrent): add unique constraint

The commit adds a new column "VAR_SCOPE_" to the table "ACT_RU_VARIABLE". This new column is
used together with the column "NAME_" for an unique constraint. This
unique constraint prevents the possibilty to add the same variable to the same
execution (or task) in a concurrent way.

related to CAM-1574
refactor(cockpit): remove status compression which is never set

- remove duplicate status tests or never set status values
- remove internal id function
- fix typos

related to #CAM-1419
fix(mssql/concurrency): add create and drop indices for mssql concurreny problems

related to CAM-1646
chore(engine): fix typo

related to CAM-2018
chore(engine/test): add commented StrongUuidGenerator for convienence
fix(mssql/concurrency): add indexes to update scripts

related to CAM-1646
feat(engine): api service access from delegation code

Makes it possible to access the process engine public API (services)
from the following delegation code:
* Java Delegate
* Execution listener
* Task listener

The process engine does not create a new command context when invoking the inner
command but instead reuse the existing command context (unless the inner command
runs through the REQUIRES_NEW chain).
fix(engine/concurrency): add indexes for mssql/db2 concurrency problems

related to CAM-1646
docs(frontend): add some code styling best practices
chore(engine): provide list of builtin resources

related to #CAM-2046
fix(cockpit/IE9): add min height to instance labels

fix CAM-2048
fix(engine/variables): change variable to byte array inside same command

Fixes referential integrity constraint violation due to wrong ordering
of inserts in dbsqlsession.

related to #CAM-2052
feat(engine-cdi): add annotation for task events

Add the following annotations:
- @CompleteTask
- @AssignTask
- @CompleteTask
- @DeleteTask

related to #CAM-2053
fix(cockpit/tree): correct text overflow

fix CAM-2049
fix(engine): no execution context for listener invocation

If task listener is invoked without atomic operation no
execution context exists. This breaks CDI business process
bean.

related to #CAM-2056
test(integration-engine): CDI task listener

related to #CAM-2053
fix(engine/sql): fix typos for db2 drop script

related to CAM-1646