Apply behaviors and styles on Sender component.

[hbulgarini]

• I think it should have a fixed size - currently, after filtering it might be reduced.

• Network label is still displayed even if all accounts from that network are filtered out.

• Would be cool if down/up arrows worked and it was possible to select an account by using down arrow + enter sequence.

• The selector should probably be fixed on top, and only the account list scrollable (also would be good to display a tiny scrollbar)

• Would be cool to add a bit of spacing between name and the balance box - it's only an issue for the longest account name on the list.

• Add the identicon of companion account as well - cause sometimes it might be easier to correlate using this identicon.

[hbulgarini]

related #168

[hbulgarini]

@tomusdrw : Add the identicon of companion account as well - cause sometimes it might be easier to correlate using this identicon.

As far is understood we replaced this by the popover right? If so, can we set this as completed?