Fix the Alarm documentation of Web API V2

Correct the Alarm example on the API documentation to contain a
valid Alarm sample and complete the Note section with information
about the connection between the type and rules fields of the
Alarm.

Fixes bug #1245362

Change-Id: I5fccf51b820330595a627fd0001beec2d5f7c6e3
Merge "Fix the Alarm documentation of Web API V2" into stable/havana