Add possibility to remove blockquotes in html answer

This is a follow-up of story #6301: reply to a follow-up comment by email
Part of tasks #6991: handle html format

We are able to remove all blockquote elements.

Furthemore, we can detect the citation header line (On XXX, Toto wrote:)
for mail coming from gmail. Other MUA that we tested (Apple Mail and
Thunderbird) do not identify clearly this sentence.

**Note:** This is sparta^Wnot used yet.

Change-Id: Id5fb513235e20f390754c1f1684c0f7dee49e001
tasks #7014: user cannot update a comment by email if no perms

This is part of story #6301: reply to a follow-up comment by email

Change-Id: I17ada524acc494c4b4aa76cd5620634d0b3e9444
Merge commit 'refs/changes/97/2597/3' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  Add possibility to remove blockquotes in html answer

Change-Id: I6d477854ef03588db58600999f7a62d3d3f3155b
This is Tuleap 7.1.99.18

Change-Id: Ibca8c2c7c36eef5de5adafa0254131cb6af9a45e
Merge commit 'refs/changes/98/2598/2' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  tasks #7014: user cannot update a comment by email if no perms

Change-Id: Ibc5057e8b4eaa45ae408d1e8ba4630c247a53437
This is Tuleap 7.1.99.19

Change-Id: I451e2f66305a281a4c52717977ae52bcd0480a00