Now scheds have an array of pieces

We need this to match new backbone-relational models on commons and caspa.
Right now in scheds on mongodb have all the data needed on mongo-driver.
If I need to rewrite tests just tell me.

Depends on https://github.com/inaes-tic/mbc-caspa/pull/146 and https://github.com/inaes-tic/mbc-common/pull/12