Remove signaling key from Device and AccountAttributes

...rsystems/textsecuregcm/controllers/AccountController.java

...ersystems/textsecuregcm/controllers/DeviceController.java

...spersystems/textsecuregcm/entities/AccountAttributes.java

...ava/org/whispersystems/textsecuregcm/storage/Account.java

...java/org/whispersystems/textsecuregcm/storage/Device.java

.../org/whispersystems/textsecuregcm/storage/DeviceTest.java

...extsecuregcm/tests/auth/BaseAccountAuthenticatorTest.java

...extsecuregcm/tests/controllers/AccountControllerTest.java

...textsecuregcm/tests/controllers/DeviceControllerTest.java

...extsecuregcm/tests/controllers/MessageControllerTest.java

...spersystems/textsecuregcm/tests/storage/AccountsTest.java

...tems/textsecuregcm/websocket/WebSocketConnectionTest.java