Elapsed time (age) configuration

[aksr]

Hi knopwob,
Thank you for dunst.
Since almost everything in dunst is configurable,
it would nice if elapsed time (age) color is configurable.
The thing that bothers me now is that, elapsed time looks like a part of the body of notification, mainly because it's the same color. I think its optional position should be defined in format (for example: _%t). I'm not sure if it's possible to implement.
Also, it would be nice if parentheses where configurable (with/without them or to change them to something else ( [ ] { } etc.), this, also would be definable in format..
_Gradition of the elapsed time would also be nice (for example: green <60s, yellow >60s, red >500s or something like that).

Thank you.

[bynect]

maybe an age_threshold_format can be added to customize it ?

Also somewhat related to #509