Fixed migration issue from #22 and #23
Fix #29 - focus on 'user' field in login screen at startup
Load and save state of archive grid
Hide 'valid' column by default
Added 'address' column hidden by default
Fixed incorrect loading of hidden columns state
Updated features list with new 'Address' column
Added distance calculation along with total and average speed - for #21
Added method that will serve CSV with positions archive - for #20
Added button to export archive to CSV - fix #20
Updated features list with 'distance' and new 'export to csv' features