Sessionstore by site

[ajay-gh]

Setting recommended:
browser.sessionstore.privacy_level = 2

Title: Do not store extra session data
Description: This preference controls when to store extra information about a session including contents of forms, scrollbar positions, cookies, and POST data. Session data could be used for fingerprinting. Meaning of values:
0 = Store extra session data for any site. (Default starting with Firefox 4.)
1 = Store extra session data for unencrypted (non-HTTPS) sites only. (Default before Firefox 4.)
2 = Never store extra session data.
Few secure sites do require session data (=0) to function properly.

See https://http://kb.mozillazine.org/Browser.sessionstore.privacy_level
for more details.

[mattia-b89]

related to: #264

[allo-]

This was implemented in eff9ab0. For further discussion see #264