Rename ambiguous datastoreTasks
Add airspace get_url
Change to get latest date
Add download_latest function
Change to downloading nav text file
Add process_nav_file method
Add vars and methods to deal with legacy nav format
Add helper parsing methods
Extract information from navaid file
Make download_latest_nav a task
Make process_nav_file a task
Fix PEP errors
Add new tasks to celery config
Store navaid in database
Parse y/n fields as boolean
Add valid date to navaid record
add country to navaid record
Change insert to upsert
Merge branch 'airspace-database' into develop

Closes #12