[scripts] Put unused scripts in scripts/old folder

scripts/mavlink_client/Makefile

scripts/mavlink_client/README.md

scripts/mavlink_client/continuous_tx.c

scripts/mavlink_client/mavlink_demo_rx.c

scripts/mavlink_client/mavlink_demo_tx.c

scripts/mavlink_client/plot.py

scripts/mavlink_client/rs232.c

scripts/mavlink_client/rs232.h

scripts/old/anakin.sh

scripts/old/anakin_client_curses/.gitignore

scripts/old/anakin_client_curses/Makefile

scripts/old/anakin_client_curses/client.c

scripts/old/excel_eventgen/EventFunctions.cpp.template

scripts/old/excel_eventgen/Events.h.template

scripts/old/excel_eventgen/README.md

scripts/old/excel_eventgen/Topics.h.template

scripts/old/excel_eventgen/credentials.json

scripts/old/excel_eventgen/event_generator.py

scripts/old/gen_fault_headers.py