add ImportTools::PostgresHandler
add ImportTools module
use ImportTools in Wdpa::Importer
Merge pull request #74 from unepwcmc/maintenance-mode

Maintenance mode
Merge branch 'add-import-tools' into add-redis-handler
add ImportTools::RedisHandler
Merge pull request #73 from unepwcmc/add-import-tools

Add import tools
add ImportTools::Import
remove responsibilities from WdpaImportWorker
make ImportTools use ImportTools::Import
add last_import to ImportTools and have S3PollingWorker use it
adapt Wdpa::Importer to new structure
update WdpaImportWorker
fix issue with blocks passing in PostgresHandler. Not testable
make import workers subclasses of ImportWorker
improvements to import.rb
add tests for ImportWorker
ensure jobs are finalised at end of ImportWorker's
add comparison of jobs for finalisation of import
add ImportTools::MaintenanceSwitcher