[2.0] Require min OR max for graph y axis domain

[sinnlosername]

Proposal:
Require a min or a max y axis domain for a graph, instead of min and max.

Current behavior:
There needs to be a min and max when using a custom y axis domain

Desired behavior:
Require only one of the two and set the other one automatically.

Alternatives considered:
None

Use case:
There are many use cases where it is good to start/end a graph at a certain point. For example when displaying latency (ping), the graph should always start at 0, but the end shall vary accordingly to the highest latency