Add tagging functionality to the address book

[erler]

I'm submitting a ...

• Bug report
• Feature request
• Support request
• Other

What is the motivation for changing the behavior?
Having talked to power users who have hundreds of addresses in their address book, an address tagging capability would enable them to organise their addresses and eg. multisig set ups more efficiently. Yet tags are flexible enough to be used for a variety of use cases. Eg. you could make the point to remove the "favourite star" from the UI component, because you could just add a "favourite" tag.

What is the current behavior and expected behavior?
The current search box says "filter by name and tags", but it is unclear where the tags come from. I haven't come across any account with a tag.

I'd imagine a user being able to add a tag via the context menu. (Note: I didn't recreate the current Apps styling here; interaction would be the same though)

And then a user would be able to filter by clicking of the corresponding badges or search for tags. (Again I used a different styling in the mockup; styling and different app navigation can be ignored)