Possible to use a single multiple value select widget?

I have the same need on a project, so here is the patch :)

I tested this patch & it works well.

- I switched the field storage configuration from allowing 1 value to unlimited values
- I checked the way the field is being displayed in single and multiple mode

@goron thanks for the report. @marjina-constantin and @batigolix: thanks for the good work. Sorry for the delay in merging.

Automatically closed - issue fixed for 2 weeks with no activity.