dynamic nested catalogs for queryables

[sbrunato]

To help with queryables handling, generate dynamic nested catalogs from a given collection using queryables with possible values. User will be able to follow a new link from a collection each time a selects a new parameter for his request:

• first http://127.0.0.1:8000/collections/foo
• then http://127.0.0.1:8000/catalogs/foo/param1:value1
• then http://127.0.0.1:8000/catalogs/foo/param1:value/param2:value2

Each catalog having links for:

• children catalogs for each available value
• queryables associated to the selected parameters
• item if available