Implement IPlacesService

[AlexBulankou]

Review: https://github.com/stopbystop/sbs-app/blob/master/README.md

Implement IPlacesServices on PlacesService. Method descriptions are in interface definition file. Then start using new service in https://github.com/stopbystop/sbs-app/blob/master/src/web/Controllers/PlaceController.cs.

• Every method should be fully covered by unit tests
• Places service should load city entries by calling GetGeoPlacesFromEmbeddedFile in constructor and cache them in memory after that.
• FindPlacesByPartialMatch for 10 results should return the same list of cities as this call.
• FindPlacesByPartialMatch should use a Trie data structure that is storing the city entries by starting letters, here's a visual example from wiki article:
  
  This way to get the results matching the input is a matter of going to the prefix from the top, then traversing the subtree and ordering the results by populating in descending order.
• FindPlacesInArea should be using efficient data structure, so that we are partitioning cities efficiently and only look at required partitions around the center location. It should not be iterating over all results.
• No external libraries should be used. If you would like to use one, check with @AlexBulankou first

This task has 2 parts:

1. Implement FindPlacesInArea and GetLocationFromPlaceID
2. Implement FindPlacesByPartialMatch