implement drop list in popover

[ChristianSch]

we need to implement a way to list the drops. cool would be:

• small thumbnail (see: http://stackoverflow.com/questions/28636622/how-to-load-image-in-swift-using-alamofire)
• title
• date of dropping
• views (later)

for that we'd need to implement a custom nstableview, nstablecellview, and delegate. I already added a nstableview with transparent background and stuff: 172328484b1d29414eb45d353b4b1232854088a7

[ChristianSch]

wee also need to sync on new drops (or just push them after GET'ting details on the new drop or smth)

[ChristianSch]

the current status quo fits the criteria for a preliminary release; moving the rest to another milestone

[ChristianSch]

Another thing to think about:

• we should have a loading animation while fetching the drops after the user signed in
• show a message if not logged in
• show a message if there are no drops