Add a few more features to Random

[MarkOates]

Namely:

• [x] get_random_element - return a random element from a stl container, exists in AllegroFlare::Useful but should be moved to Random (added in https://github.com/allegroflare/allegro_flare/commit/e248728c23f9bcd42fca49aafbf35f80eae1d719)
• [x] get_random_color_exhaustive - would return a random color without repeating a color until all colors have been returned (added in https://github.com/allegroflare/allegro_flare/commit/3e17fb18c10d4b3d87ec5bdba2a8203fe80dd274, but needs test)
• [x] shuffle - shuffle an array of elements (could be a template) (added in https://github.com/allegroflare/allegro_flare/commit/e7f135d8b46af95b6318f681c8967c17ebb2977b, but needs tests)
• [x] Also, there are a few more random functions in Useful that should be audited to be moved to Random.

[MarkOates]

All the remaining Useful randoms were added through these changes. They should be removed from Useful now.

[MarkOates]

This is done, but there's 3 tests that need to be finished. Also, items should be removed from Useful.

I created an issue for the 3 tests to finish, and an issue to remove the Useful randoms.