Move tests to relevant subprojects (#615)

- Moved test projects to the parent project they belong to
- Improved test stability/corectness
- Improved recursive directory deletion by safely ignoring current- and parent-directory entries.
- Update docs

TactilityFreeRtos/Tests/Source/RecursiveMutexTest.cpp

@@ -0,0 +1,40 @@
+#include "doctest.h"
+#include <Tactility/kernel/Kernel.h>
+#include <Tactility/RecursiveMutex.h>
+#include <Tactility/Thread.h>
+
+using namespace tt;
+
+TEST_CASE("a RecursiveMutex can block a thread") {
+    auto mutex = RecursiveMutex();
+    CHECK_EQ(mutex.lock(kernel::FREERTOS_MAX_TICKS), true);
+
+    Thread thread = Thread(
+        "thread",
+        1024,
+        [&mutex] {
+            mutex.lock(kernel::FREERTOS_MAX_TICKS);
+            mutex.unlock();
+            return 0;
+        }
+    );
+    thread.start();
+
+    kernel::delayMillis(5);
+    CHECK_EQ(thread.getState(), Thread::State::Running);
+
+    mutex.unlock();
+
+    kernel::delayMillis(5);
+    CHECK_EQ(thread.getState(), Thread::State::Stopped);
+
+    thread.join();
+}
+
+TEST_CASE("a RecursiveMutex can be locked more than once from the same context") {
+    RecursiveMutex mutex;
+    CHECK_EQ(mutex.lock(0), true);
+    CHECK_EQ(mutex.lock(0), true);
+    mutex.unlock();
+    mutex.unlock();
+}