NMS-7197: Create Ops Board documentation

 - Created file and folder structure
 - Created screenshots and drafts for basic concepts of Ops Board, Ops Panel and Dashlet
 - Created generic behavior for the Criteria component to filter for Alarms and Alarm Details
 - Created generic documentation about the boost behavior of a Dashlet
 - Created description for all available Dashlets

JIRA: http://issues.opennms.org/browse/NMS-7197

Todo Review:
- [ ] Typo and grammar
- [ ] Formatting and conventions
- [ ] Content

@christianpape Can you add the priority behavior and an example?