href-to should respect current state query parameters

[bekharsky]

Useful for combined filters. For example:

default route params: tag: 'all', from: '2016-04-07', to: '2016-04-08', fav: 'yes'

current state route params: tag: 'vip', from: '2016-04-01', to: '2016-04-02', fav: ''

How link-to works:

    {{link-to
      'prev'
      'games'
      (query-params from=ydEx to=ydTo)}}

result url: games?from=2016-04-06&to=2016-04-07&fav=&tag=vip

How equivalent href-to works:

<a href='{{href-to 'games' (query-params from=ydEx to=ydTo)}}'>prev</a>

result url: games?from=2016-04-06&to=2016-04-07&fav=yes&tag=all