feat(engine): refactor identity, add authorization

- cleanup identity service implementation preparing LDAP support:

    * extract SPI Interface ReadOnlyIdentityProvider &
      WritableIdentityProvider
    * deprecate *-account methods in Identity Service
    * add read-only checks in identity service
    * user picture is now saved using IdentityInfo (making it possible to
      link LDAP users to pictures later on)

- add initial cut of authorization service
    * add authorization entity
    * add authorization query

related to #CAM-978 #CAM-979
feat(identity): add ldap identity service

- add ReadOnlyIdentityProvider implementation backed by ldap repository.
- testsuite uses apache open directory

related to #CAM-978
wip(engine): add password hashing

- passwords are now stored as base64 encoded SHA hashes

related to #CAM-980
feat(rest): add user & group rest service

- Add user rest service
- Add group rest service

related to #CAM-957, #CAM-958
feat(engine): add DB scripts for authorizations

- add create/drop scripts for ACT_RU_AUTHORIZATION table on all databases

RELATED TO #CAM-979
feat(engine): add orderBy in Auth query

- add support for orderBy in authorization query

related to #CAM-979
Merge branch 'master' into new-identity
chore(identity): add configurability for ldap port

- add support for configuring the LDAP server port through the maven build

related to #CAM-978
doc(engine): improve authorization javadocs

related to CAM-979
Merge branch 'master' of github.com:camunda/camunda-bpm-platform
chore(build): remove ldap from check-engine

- remove identity-ldap from check engine profile