Rapid NumberEntity increment / decrement causes value override

[DanielBaulig]

This fundamentally probably also applies to other entities, but it's very apparent on NumberEntity, when using the up/down arrows.

Since NumberEntity uses set(v) to set the new value, the value used to update the entity is the most recent value displayed in the ResponsiveInput. This is fine, until multiple updates are queued and the new values return asynchronously causing the input to jump back to older values while still incrementing/decrementing.

I see two ways how to solve this:

1. Implement a decrement/increment method in web_server that can increment/decrement the NumberEntity by a specific amount independent from it's current value. Note that this would still cause the input to "flicker" in value, but would have eventual consistency.
2. Implement some form of optimistic/delayed update that disregards state updates while we are still awaiting "responses" from previous state updates. It's not clear at this point how to cleanly and reliably implement this.