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

TactilityKernel/tests/source/time_and_delay.cpp

@@ -0,0 +1,30 @@
+#include "doctest.h"
+#include <tactility/delay.h>
+#include <tactility/time.h>
+
+TEST_CASE("delay ticks should be accurate within 1 tick") {
+    auto start_time = get_ticks();
+    delay_ticks(100);
+    auto end_time = get_ticks();
+    auto difference = end_time - start_time;
+    CHECK_EQ(difference >= 100, true);
+    CHECK_EQ(difference <= 101, true);
+}
+
+TEST_CASE("delay millis should be accurate within 1 tick") {
+    auto start_time = get_millis();
+    delay_millis(100);
+    auto end_time = get_millis();
+    auto difference = end_time - start_time;
+    CHECK_EQ(difference >= 100, true);
+    CHECK_EQ(difference <= 101, true);
+}
+
+TEST_CASE("microsecond time should be accurate within 1 tick") {
+    auto start_time = get_micros_since_boot();
+    delay_millis(100);
+    auto end_time = get_micros_since_boot();
+    auto difference = (end_time - start_time) / 1000;
+    CHECK_EQ(difference >= 99, true);
+    CHECK_EQ(difference <= 101, true);
+}