RSK: implement sorting on empty query string

[ntarocco]

• introduces a new prop to define which sorting to use on empty query string
• adds a new private app state to the store to keep track if the user has selected a new sorting and what was the initial sorting before change
• adds tests
• changes documentation
• closes #111

[zzacharo]

I ran the branch locally and noticed that when you enter a query and then change the sorting and clear the query the last sorting is used in the empty query. Is this the desired behavior or everytime an empty query is entered the sorting should change to the defaultOnEmptyString?

I would say that everytime the query string is empty the defaultOnEmptyString should be used :)

[ntarocco]

I ran the branch locally and noticed that when you enter a query and then change the sorting and clear the query the last sorting is used in the empty query. Is this the desired behavior or everytime an empty query is entered the sorting should change to the defaultOnEmptyString?

I would say that everytime the query string is empty the defaultOnEmptyString should be used :)

Good question @KonstantinaStoikou @zzacharo how I have implemented is:

• nothing touched, no query string: use sorting given via config onEmptyQuery
• nothing touched, with query string: use default sorting
• user changed sorting (user choice), independently of the presence of the query string: use user choice

The idea was that if the user selects a sorting, it means (s)he wants that. If I choose sort by most loaned, I am not sure I wanted to be automatically changed back to most recent or bestmatch. WDYT?