.htaccess block management

[codeling]

Continueing from https://github.com/codeling/bfstop/issues/74.

In the backend, administrators should be able to manage blocks via .htaccess:

• show blocked IPs in backend
• allow unblocking

[codeling]

Fixed by https://github.com/codeling/com_bfstop/commit/db02be251a97c31f147ad89063a983f3a4c0bab4. Still open:

• disable editing of .htaccess entries (currently leads to an invalid form)
• full support for ordering the list. currently, htaccess entries are always last, and are sorted the same way as in the .htaccess file (the rest of the entries heed the specified sorting order)