share: add prefix/param for shared field in location hash

[pamfilos]

Right now the shared fields are displayed and added to the location like:
http://localhost/#root$item_pkd44k$item_dprmi9

It is better to:

• add prefix (e.g. shared_field => http://localhost/#shared_field=root$item_pkd44k$item_dprmi9 ).
  >>> this way we can allow for multiple functions of the location hash (e.g. if an app already utilizes hash locations, our functionality can be added on top, etc)
• maybe support for multiple selections?