add Google translate client

[thataboy]

translates selected text in reader view; may be invoked from Applications menu in stand alone mode

Built and tested. Based on commit 0f7fdea597a9d2e557c25f37c772f660433ef74a from upstream.

Notes:

1. I needed to modify SearchBar to allow omitting the search context menu. This unfortunately adds more diffs to their already large number. Je m'excuse.

2. I don't know if there's a better way to include reqwest in Cargo.toml

3. FIXED The way I'm obtaining wifi is hacky. When context.online is false, I turn wifi off and back on to ensure I get notify on NetUp.