Cleanup and improvements (#194)

- Lots of changes for migrating C code to C++
- Improved `Lockable` in several ways like adding `withLock()` (+ tests)
- Improved `Semaphore` a bit for improved readability, and also added some tests
- Upgrade Linux machine in GitHub Actions so that we can compile with a newer GCC
- Simplification of WiFi connection
- Updated funding options
- (and more)

Tests/TactilityCore/MutexTest.cpp

@@ -32,3 +32,22 @@ TEST_CASE("a mutex can block a thread") {
 
     thread.join();
 }
+
+TEST_CASE("a Mutex can be locked exactly once") {
+    auto mutex = Mutex(Mutex::Type::Normal);
+    CHECK_EQ(mutex.lock(0), true);
+    CHECK_EQ(mutex.lock(0), false);
+    CHECK_EQ(mutex.unlock(), true);
+}
+
+TEST_CASE("unlocking a Mutex without locking returns false") {
+    auto mutex = Mutex(Mutex::Type::Normal);
+    CHECK_EQ(mutex.unlock(), false);
+}
+
+TEST_CASE("unlocking a Mutex twice returns false on the second attempt") {
+    auto mutex = Mutex(Mutex::Type::Normal);
+    CHECK_EQ(mutex.lock(0), true);
+    CHECK_EQ(mutex.unlock(), true);
+    CHECK_EQ(mutex.unlock(), false);
+}