Option to provide pre-selected items

[Nitin Hayaran]

Currently there is no way to provide pre-selected items.

Possible use case:
If we save selected options on backend, then ideally Picker should be loaded with pre-selected options.

[Chen Zeyu]

I think I figured out how to do it properly, will add soon.

[Chen Zeyu]

added - (void)setSelectedRows: (NSArray *)rows; in 0.3.6