added the "initprovider" command to initialize the database structure.
If we change the database schema the required changes will be checked
at startup and automatically applyed.
Login can be restricted to specific ranges of IP address or to a specific IP
address.
Please apply the appropriate SQL upgrade script to add the filter field to your
database.
The filter database field will allow to add other filters without requiring a
new database migration
we can now have permissions such as these ones
{"/":["*"],"/somedir":["list","download"]}
The old permissions are automatically converted to the new structure,
no database migration is needed
an user can now be disabled or expired.
If you are using an SQL database as dataprovider please remember to
execute the sql update script inside "sql" folder.
Fixes#57
