Investigate using Thunderbird & TorBirdy as the RSS reader

This should be done against the questions raised in https://trac.torproject.org/projects/tor/wiki/torbirdy#IsitsafetosubscribetoRSSfeedswithThunderbirdandTorBirdy:

• Is automatic fetching disabled?
• Is HTML disabled?
• Is JavaScript disabled?
• Are proxy settings respected? (this is out of scope as far as Tails is concerned so not stricly required as part of this ticket)
• Are there other anonymity implications?

• Sukhbir said he started working on this already, and created https://trac.torproject.org/projects/tor/ticket/19031 to track this.
• anonym answered he would have time to work on this any time soon.

Parent Task: #11082 (closed)

Related issues

• Related to #5663 (closed)
• Related to #7625 (closed)
• Related to #11399 (closed)

Original created by @intrigeri on 7626 (Redmine)