Refactored search string builder to new class

The new urlbuilder class will contain all methods for building the
request url, to enable better unit testing
Work on the urlbuilder class and unit tests

Changes to the urlbuilder test as part of refactoring and unit tests
created to prove functionality is as expected.
Addition unit tests for URLBuilder class

More unit tests have been added and some changed have been done in
URLBuilder class to pass them.
Solution  refactoring

Changed structure of solution so tests are more logically organized.