Integrating Peter Fleury's HD44780 LCD library (#3209)

* integrated Peter Fleury's LCD library for HD44780 LCDs

* fixed typo

* cleanup finished

* add documentation

* added HD44780 documentation

* removed keyboard from .gitmodules

* resolved merge conflict

* removed edit of kira75s rules.mk made by merge

* moved hd44780 to drivers/avr

* Added licence info to hd44780 files

* Added link to hd44780 docs.

tmk_core/common/keyboard.c

@@ -69,6 +69,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #ifdef MIDI_ENABLE
 #   include "process_midi.h"
 #endif
+#ifdef HD44780_ENABLE
+#   include "hd44780.h"
+#endif
 
 #ifdef MATRIX_HAS_GHOST
 extern const uint16_t keymaps[][MATRIX_ROWS][MATRIX_COLS];