Keyboard improvements (#240)

- Renamed various keyboard functions so it's easier to differentiate hardware versus software keyboard functionality
- Created `Tactility/lvgl/Keyboard.h` as a proxy  for the internal `Gui` service.
- Implemented `tt_lvgl_keyboard.h` in `TactilityC`.

TactilityC/Source/tt_lvgl_keyboard.cpp

@@ -0,0 +1,37 @@
+#include "Tactility/lvgl/Keyboard.h"
+
+extern "C" {
+
+void tt_lvgl_software_keyboard_show(lv_obj_t* textarea) {
+    tt::lvgl::software_keyboard_show(textarea);
+}
+
+void tt_lvgl_software_keyboard_hide() {
+    tt::lvgl::software_keyboard_hide();
+}
+
+bool tt_lvgl_software_keyboard_is_enabled() {
+    return tt::lvgl::software_keyboard_is_enabled();
+}
+
+void tt_lvgl_software_keyboard_activate(lv_group_t* group) {
+    tt::lvgl::software_keyboard_activate(group);
+}
+
+void tt_lvgl_software_keyboard_deactivate() {
+    tt::lvgl::software_keyboard_deactivate();
+}
+
+bool tt_lvgl_hardware_keyboard_is_available() {
+    return tt::lvgl::hardware_keyboard_is_available();
+}
+
+void tt_lvgl_hardware_keyboard_set_indev(lv_indev_t* device) {
+    tt::lvgl::hardware_keyboard_set_indev(device);
+}
+
+void tt_lvgl_keyboard_add_textarea(lv_obj_t* textarea) {
+    tt::lvgl::keyboard_add_textarea(textarea);
+}
+
+}