Extract parsoid host and pagebundle retrieval
Extract parsoid host and pagebundle retrieval

This is part of a general effort to refactor the code, with an eye
toward both configurability and modularity.

wikimedia/mediawiki-services-restbase,wikimedia/hyperswitch,wikimedia/restbase,gwicke/restbase,hardikj/restbase,wikimedia/mediawiki-services-restbase,d00rman/restbase,cscott/restbase,physikerwelt/restbase,eevans/restbase,inverno/restbase,milimetric/restbase,inverno/restbase,Pchelolo/restbase,physikerwelt/restbase,eevans/restbase,milimetric/restbase,cscott/restbase,Krenair/restbase,Pchelolo/restbase,gwicke/restbase,d00rman/restbase,hardikj/restbase,Krenair/restbase,wikimedia/restbase