Ability to use all widgets in dashboard templates

Currently some types of widget cannot be used for templated dashboards. It is rather artificial limitation that should be eliminated. We should allow all widgets to be used everywhere. It affects the following widgets:

1. Action log
2. Discovery status
3. Favourite graphs
4. Favourite maps
5. Geomap
6. Graph
7. Host availability
8. Map
9. Map navigation tree
10. Problem hosts
11. Problems
12. Problems by severity
13. SLA report
14. System information
15. Top hosts
16. Trigger overview
17. Web monitoring