Create filter screen

[lorenzoPrimi]

• New filter button where the BTC logo is.
  
  

• Make communities more visible

Now you can access the communities page by tapping on the Bitcoin logo or opening the menu and tapping Communities.
Both are not very intuitive.
Changing the bitcoin to another icon could be a good starting point

[lorenzoPrimi]

I'm a bit struggling with the code, but the filter screen has been created here:
https://github.com/teambtcmap/btcmap-ios/tree/home_screen
What is still left do to is to add the count for every single item (ATMs, Bars...) and actually apply the filters when they are enabled or disabled.