Added Support for /3/person/popular

Created GetPersonList methods in TMDbClientPeople as similar to
GetMovieList in TMDbClientMovie to support the person/popular api get
request.

Added necessary classes for the deserialization of the REST response; as
well as an enumeration describing the PersonListType (for now, we only
have 'Popular') - this resembles MovieListType.
Added TestPersonList

Added a test case for GetPersonList method in TMDbClientPeople.
Test case mirrors TestMovieList, but for People.
Removed Language Parameter in GetPersonList

TMDb API does not publicize an optional language parameter for
person/popular
Added support for /3/person/latest

Created GetPersonItem method in TMDbClientPeople to support the
person/latest api get request.

Created an enumeration describing the PersonItemType (for now, we only
have 'Latest') - this resembles MovieListType / PersonListType.

Note that this is a different method to GetPersonList because /latest
only returns a single person, rather than a list of people (thus it is
not wrapped in a SearchContainer).

Added TestPersonItem to test this new method.
Corrected Namespaces

Corrected Namespaces on PersonItemType and PersonListType.

Also renamed
TestPersonList to TestPersonsList; and
TestPersonItem to TestPersonsItem

to match current convention