Remove total_sites from SiteCollection.expand

[Michele Simionato]

Each SiteCollection object has a method site_coll.expand(data, total_sites, placeholder) expanding the array data on the sites in site_coll and returning an array of size total_sites. The typical use case is the expansion of values relative to a filtered site collection. If we give to the filtered site collection the knowledge of total_sites before the filtering, then the parameter does not need to be passed and the API can be simplified. Damiano agrees that it is a good idea.

[Michele Simionato (michele-simionato)]

https://github.com/gem/oq-hazardlib/pull/165