Cookie management

[miglen]

Control panel with cookie management for the current session.
All cookies must not be saved locally, but transparent.

[miglen]

Cookie management landed in #51 (merged into master). The Cookies tab on the entry form now supports per-cookie delete, an add-cookie name/value form, and a Clear all button. Settings cookies (flags, userAgent, PHPSESSID) and hdr_* header cookies are kept out of the user-facing list. Closing — if you want per-target cookie injection or a richer cookie editor later, please open a fresh issue with the specific use case.