- add main_component_uuid temporary columns to CE_QUEUE
- add main_last_key and main_component_uuid columns to CE_ACTIVITY
- back to initial paradigm in Compute Engine: even for branches/PRs, the row in table PROJECTS a task belongs to is created in api/ce/submit
- add main component concept to CeTask
- improved consistency check when processing a report task to account for row in PROJECTS now being the one of the branche/PR
- stronger validation of characteristics passed to api/ce/submit
- add api/system/migrate_data for SonarCloud online data migration