The updated IntroActivity

The updated IntroActivity that's now useing the changes from the
previous commits.
Added an abstract Place class

Added an abstract Place class that's supposed to be the super class for
all places in the application. It'll allow easier handling of the places
coordinates.
Added a Coordinates class

The class will be used to get a place's coordinates.
Updated the Institution class to extend Place

The Institution class now extends Place instead of Model.
Added a new class to represent POIs

Added a new class to represent points of interest.
Added a method to get all the POIs of a city
Fixed coordinates retrieval in Institution
Removed the abstract method from Place...

... since it's not longer needed.
Added type and imageUri members to the POI class

Also added a method to get the POIs list of coordinates, although a POI
will probably only have one coordinate.
Decided to make City a Place as well
Added the Wisdom class

The Wisdom class will represent reviews of people that have already had
an exchange in the given city or institution.