fix(dropdowns): dropdown should close correctly when used in modals (fixes #267, fixes #221)

[mkjeff]

fixed Dropdown does not work on angular2-modal #267
fixed dropdown button auto closes #221
changed ButtonRadio.btnRadio to be able to hold any object

[valorkin]

I believe it should work for ng2-modal
let me see, what can be done
may be modal component should be changed

[valorkin]

@mkjeff ok, now looks even better

1. leave here only dropdown fixes
   buttons will be updated when this will be fixed: Angular 2 template driven form radio button not working angular/angular#7642
2. could you please squash commits while rebasing on top of master? :)
   and name it
   fix(dropdowns): dropdown should close correctly when used in modals (fixes #267, fixes #221)

When done, drop a note here, so I will test and merge it ASAP
Thanks in advance :)

[mkjeff]

@valorkin had sorted out my commits

[valorkin]

Awesome! Merging