Implement unit testing (#30)

- Create `test` and `tactility-core-tests` subprojects
- Created tests for `thread.c`
- Fixed issue with thread cleanup (see what I did there? :P)
- Removed functions from `thread.h` that did not exist anymore
- Updated `ideas.md`

tests/tactility-core/main.cpp

@@ -0,0 +1,58 @@
+#define DOCTEST_CONFIG_IMPLEMENT
+#include "doctest.h"
+#include <cassert>
+
+#include "FreeRTOS.h"
+#include "task.h"
+
+typedef struct {
+    int argc;
+    char** argv;
+    int result;
+} TestTaskData;
+
+void test_task(void* parameter) {
+    auto* data = (TestTaskData*)parameter;
+
+    doctest::Context context;
+
+    context.applyCommandLine(data->argc, data->argv);
+
+    // overrides
+    context.setOption("no-breaks", true); // don't break in the debugger when assertions fail
+
+    data->result = context.run();
+
+    if (context.shouldExit()) { // important - query flags (and --exit) rely on the user doing this
+        vTaskEndScheduler();
+    }
+
+    vTaskDelete(NULL);
+}
+
+int main(int argc, char** argv) {
+    TestTaskData data = {
+        .argc = argc,
+        .argv = argv,
+        .result = 0
+    };
+
+    BaseType_t task_result = xTaskCreate(
+        test_task,
+        "test_task",
+        8192,
+        &data,
+        1,
+        NULL
+    );
+    assert(task_result == pdPASS);
+
+    vTaskStartScheduler();
+}
+
+extern "C" {
+    // Required for FreeRTOS
+    void vAssertCalled(unsigned long line, const char* const file) {
+        __assert_fail("assert failed", file, line, "");
+    }
+}