Implement range bans (#478)

* Implement range bans

People connecting from banned IP ranges are unable to upload
torrents anonymously, and need to manually have their accounts
activated.

This adds a new table "rangebans", and a command line utility,
"rangeban.py", which can be used to add, list and remove rangebans
from the command line.

As an example:

./rangeban.py ban 192.168.0.0/24

This would rangeban anything in this /24.

The temporary_tor column allows automated scripts to clean out and
re-add ever-changing sets of ranges to be banned without affecting
the other ranges.

This has only been tested for IPv4.

* Revise Rangebans

Add an id column, and change "temporary_tor" to "temp". Also
index masked_cidr and mask.

* rangebans: fix enabled and the binary op

kill me

* Add enabling/disabling bans to rangeban.py

* rangebans: fail earlier on garbage arguments

* rangebans: fix linter errors

* rangeban.py: don't shadow builtin keyword 'id'

* rangebans: change temporary ban logic, column

The 'temp' column is now a nullable time column. If the field is
null, the ban is understood to be permanent. If there is a time
in there, it's understood to be the creation time of the ban.

This allows scripts to e.g. delete all temporary bans older than
a certain amount of time.

Also, rename the '_cidr_string' column to 'cidr_string', because
reasons.

* rangeban.py: use ip_address to parse CIDR subnet

* rangebans: fixes to the mask calculation and query

Both were not bugs per-se, but just technically not needed/correct.

* De-meme apparently

nyaa/forms.py

@@ -349,6 +349,7 @@ class UploadForm(FlaskForm):
     ])
 
     ratelimit = HiddenField()
+    rangebanned = HiddenField()
 
     def validate_torrent_file(form, field):
         # Decode and ensure data is bencoded data