clean up
use LyricsApiBase instance to get db adapter config
WIP; added method to get recent changes, a unit tests
WIP; added grouping by deletions and others, some unit tests
removed hardcoded date, added one more test case for rc_cur_id === 0
removed method which is not needed
page ids is everything we need right now
deleted an unnecessary method and removed tests for it, started working on updates
Merge branch 'dev' into lyrics-api-update-index
added getConfig() method because we resigned from LyricsApiBase::getConfig() approach
WIP: removed article category setters and getters, added new method which gets only artist pages
WIP: added new method getArtistPageId() which is used to change results with recently changed pages to an array with artist pages only
added some unit tests
added more logging
fixes in convertIntoArtistPages(), changes in getArtistPageId() and one more unit test case added
fixed SolrAdapter::saveArtist()
added deleting methods
refactored deleting docs code a little bit
removed scraping an article - we base on artists articles only
no need to keep DatabaseAdapter abstraction; we stay with SolrAdapter only