force to delete volume #165
Merge branch 'master' into forceDelete

Conflicts:
	core/src/main/java/org/openstack4j/api/storage/BlockVolumeService.java
	core/src/main/java/org/openstack4j/openstack/storage/block/internal/BlockVolumeServiceImpl.java
Issue #181
Issue #175
Issue #182
Merge pull request #180 from octupszhang/forceDelete

Force delete volume support
constants
Update CONTRIBUTING.md
Update CONTRIBUTING.md
add domain id to user class
Merge origin/master

Conflicts:
	core/src/main/java/org/openstack4j/openstack/identity/domain/KeystoneUser.java
Merge origin/master

Conflicts:
	core/src/main/java/org/openstack4j/openstack/identity/domain/KeystoneUser.java