move mass unit conversion into util and add tooltip event

[alex-s168]

title

I did this because I need to display mass values in item tooltips in Tournament and other addons might want to do similar things

I'm not really happy with the mass tooltips ("old" feature) beeing in the main mod class, but I don't know where to move the code to

[ewoudje]

Could you move the mixin in its own feature, and instead of having a even abstraction just doing it directly.
Im assuming the tooltips event is for tournament use too but VS2 isn't an util library for anything except physics. You would only be depending on stuff that could be changed anytime.

[alex-s168]

Could you move the mixin in its own feature, and instead of having a even abstraction just doing it directly. Im assuming the tooltips event is for tournament use too but VS2 isn't an util library for anything except physics. You would only be depending on stuff that could be changed anytime.

When depending on VS2, we depend on something that changes a lot anyways.
Is it bad to have more features that don't need maintaining?
also VS2 is already doing the mixin and we already have an event system.
it is almost free to combine those...