Price Change Alarm without timeframe

[dllud]

Some users have requested a Price Change Alarm without timeframe.

The reference price should be the price at the moment the alarm was created. This reference price can only change after some user input.

This would allow users to track price changes from a well-known point in time, for instance, the moment they bought or sold a given asset.

Example usage:

1. User creates the alarm. Current price is set as reference.
2. Alarm fires 6 months later (Hey! Time to sell/buy). Alarm is turned off.
3. User manually turns on the alarm. Old reference price is discarded and replaced by current price.