added new Solr-Function FieldCollapsing #3
removed field rows and start, cause already implented in Select-Class. #3
Fixed Core::count() to work with collections
Simplified error handler in logging setup
Fixed tests to account for changes in Core::count()
Added Client::factory()
Fix CLI error handling to work when no response is received
Removed Helpers\Json, replaced by Opendi\Lang\Json

fixes #4
Moved ping() from Client to Core
Merge branch 'feature/grouping' of github.com:odrescher/solrclient into odrescher-feature/grouping
minor formatting, phpdocs
Merge branch 'odrescher-feature/grouping' into develop
fixed GroupTest by removing test for rows and fixing the namespace of an exception