speed up page generation by making avatar lookup occur at the browser
not at page generation

* Protect against evil email address ".."

* hash the complete email address

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-Authored-By: Lauris BH <lauris@nix.lv>

* remove since it is there for 3years

* fix 500 error for ghost avatar

* dont insert "-1" in any case to issue.poster_id

* fix lint

* Test: ghost avatar link

* fix test

* Revert "remove since it is there for 3years"

This reverts commit fd9ad05159.

* Revert "dont insert "-1" in any case to issue.poster_id"

This reverts commit 05469ab6d8.

Co-authored-by: zeripath <art27@cantab.net>

* Always return local url for users avatar

Avoids having to wait for DNS lookups when libravatar is activated
fixing #6046

* Avoid double slash in avatar link

* Move avatar route to the correct place