Multiselect appendTo option

[vmilovan]

I'm submitting a ... (check one with "x")

[x] feature request => Implement appendTo option on Multiselect component (like dropdown).

Current behavior
Multiselect component does not have appendTo option e.g appendTo="body"

Expected behavior
It should have an appendTo option in case the multiselect overlay panel cant be displayed because
of a container like accordion.

What is the motivation / use case for changing the behavior?
We are using multiselect components inside an accordion for hinding input fields if user doesnt need them
but we need to scroll accordion in order to see all choices inside multiselect.

• PrimeNG version: 2.0.X