Add examples using basic WIMP applications and testing using GreaTest

[pzaino]

Background

Add tests that use the WIMP and GreaTest to check if everything works fine with WIMP applications.

GCC and DDE compilers are both valid for this Issue, so you can use your favourite!

Do not commit directly to main branch, instead create your own branch or fork, add your test code and test it and then ask for a PR to develop branch.

Multiple PRs for this task are ok. :)

Definition of Done

• Add test code in tests that use RISC OS WIMP interface and create at least a Window or an Icon on the iconbar
• Each test code should run some unit Testing using GreaTest library and displaying on regular screen or in !Reporter
• If you find out that GreaTest is not suitable for Unit testing when an app is using the WIMP suggest changes to solve this