Implemented XML parsing
Parsing of various fields is implemented
Implemented FlightsStorage. Revamped architecture.
Implemented table view with list of flights
Added navigationController
Implemented Detailed ViewController
Fixed description
Implemented lazy losing of detailed URL
Added “Description” field update
Main tableView deselects row on viewWillAppear
Adjusted visuals of Detailed Screen
Implemented image loading
Implemented image displaying on Detail Screen
Added network activity indicator
Added activity indicator while flights are loading
Implemented sorting by price/duration
Merge branch 'develop'

* develop:
  Implemented sorting by price/duration
  Added activity indicator while flights are loading
  Added network activity indicator
  Implemented image displaying on Detail Screen
  Implemented image loading
  Adjusted visuals of Detailed Screen
  Main tableView deselects row on viewWillAppear
  Added “Description” field update
  Implemented lazy losing of detailed URL
  Fixed description
  Implemented Detailed ViewController
  Added navigationController
  Implemented table view with list of flights
  Implemented FlightsStorage. Revamped architecture.
  Parsing of various fields is implemented
  Implemented XML parsing