Fix "format_timer" instead of "timer_format"

[Crystalwarrior]

Fix timer format and intervals not being properly set or updated
Improve timer_format documentation to be more descriptive

TODO:

• Fix larger intervals setting the timer to 0 at some steps for some reason
• Fix send_timer_set_step_length not having an AO equivalent. Should work practically the same, allowing the user to create timers ticking up.