Feature and Bug fixes

Features

• document improvements and restructuring by @royopa and @chellem
• console command solr:synchronize has now a progress-bar
• console command solr:synchronize shows which index was used, feature-request by @phphatesme

Bugfixes

• if two different documents with same Id were indexed, then the first inserted document was overwritten by the seconds
• console command solr:synchronize shows now a correct summary