Move IpCounter to date-based tmpdir storage with daily cleanup

IpCounter files were stored in the cache directory without cleanup,
causing inode exhaustion on busy sites. Files are now stored in
tmp

Move IpCounter to date-based tmpdir storage with daily cleanup

IpCounter files were stored in the cache directory without cleanup,
causing inode exhaustion on busy sites. Files are now stored in
tmpdir/captcha/ip/Y-m-d/ with automatic daily cleanup via indexer.

Also reorganizes FileCookie to tmpdir/captcha/cookie/Y-m-d/ for
consistency and moves timeout config loading into IpCounter constructor.

fixes #146

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added tests for IPCounter

adjust tests and fix file cookie handling

first go at cleaning up the code

update tests

clean up old captcha cookies

Old cookies are now cleared once per day.

adjusted tests for captcha cookies

use assertFalse

added small comment on test behavior

Don't skip tests when input is empty (guards against timing attacks)

Fix generator when random seed is zero

Test cases