Clean obsolete templates

[pdelboca]

This is part of #883 .

Notes:

• The old aldryn template is no longer required. We have our own quote plugin now.
• cms_homepage.html was cleaned in a previous PR. We are cleaninng all its snippets now (25ccf83)
• We are no using breadcrumb so there is no need for the template
• cms_article.html, cms_twocolumns.html and cms_childlist.html are no longer used.
• newsletter.html and cms_apphooks.html are gonna be cleaned after migrating our members pages to CMS content. I added a note in the template for future reference.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c8edbb6) 88.61% compared to head (8729851) 88.61%.

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Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1032   +/-   ##
========================================
  Coverage    88.61%   88.61%           
========================================
  Files           97       97           
  Lines         1203     1203           
  Branches        49       49           
========================================
  Hits          1066     1066           
  Misses         135      135           
  Partials         2        2           

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