Improving possibility to filter by google issues status values.
Added default labels to LABEL_MAPPING.
Moved class MergedIntoUpdate below settings section and removed blank line between comment and variable in the settings section.
Moved variables in settings section.
Added default states to STATE_MAPPING and moved variables in settings section.
Renamed STATE_MAPPING and LABEL_MAPPING to GOOGLE_STATUS_MAPPING and GOOGLE_LABEL_MAPPING.