Rephrase "Copy from a friend" and "Install from scratch"

From the user testing and the discussion on terminology we had several issues and ideas to improve on the current phrasing:

• “Scratch” was sometimes hard to understand.
• “Clone” is probably ok, by “copy” is more common.

For “Copy from a friend”:

• Clone from a friend
• Copy from Existing Tails Media
• Copy from another Tails

For “Install from scratch”:

• Install from the Internet
• Download and install

See:

• https://mailman.boum.org/pipermail/tails-ux/2015-May/000414.html
• https://mailman.boum.org/pipermail/tails-ux/2015-May/000419.html

Feature Branch: web/assistant

Parent Task: #9445 (closed)

Related issues

• Related to #8866 (closed)

Original created by @sajolida on 9433 (Redmine)