Display images, notes, sources for events as collapsible tabs

[czifumasa]

Hi, after sometime I decided to come back to this awesome project.

In my pull request, I'd like to expand details panel. This time I am focusing on events. Gedcom format allows storing a lot of additional data with event entries. Till know Topola-viewer did not most of them. With my changes it will be possible to access:

• images
• notes
• sources/citations

Extra data is presented in collapsible tabs, represented by icons. When details panel is opened all tabs are collapsed. User can click on icon to expand content of the tab. This way details panel is still compact and not overloaded with bunch of content. Extra info is accessible only on demand.

Functionality has been implemented with gramps-plugin users in mind, but as along as event entry is complaint with Gedcom specs it should work for files created with other software as well. Example gedcom from Gramps documentation can be used to play around with this new feature: Zip file with example gedcom

[PeWu]

This looks great! I added a couple of minor suggestions as comments above.

[czifumasa]

Thank you for review, I applied suggested changes

[PeWu]

Thank you!