Explore button + ability to run individual tests

[khaledmousa]

This change addresses #29, #14, and #46

An "Explore" button is added to the Summary View. This opens a list of tests grouped by class (my initial intention was to have a dropdown which will allow grouping by Category, Class, Assembly, etc., but I am not sure I'll have the time to include this). Double-tapping a test will run it and show the results in the Summary page.

New ViewModels:

• TestExplorerViewModel - this is the main viewmodel bound to the test explorer view
• TestDescriptionViewModel - view model representing a single test case
• GroupedTestsViewModel - view model representing a set of test cases in the same group

New Views:

• TestExplorerView - test explorer view

Screenshots:

1. Updated summary view

2. Explore view

[dnfadmin]

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