Fix html deprecations

[jbrichau]

Removes the use of tags and attributes currently deprecated (or non-functioning) in HTML5 from the Seaside tests and examples.

Also fix the wrong deprecation of:

• the th.scope attribute (it was only deprecated for td tags).
• the charset attribute on meta tags

Fixes #1418

[codecov]

Codecov Report

Attention: Patch coverage is 77.41935% with 7 lines in your changes missing coverage. Please review.

Project coverage is 49.04%. Comparing base (d90609c) to head (ad52bec).

Files	Patch %	Lines
...Test.class/instance/renderInline.factor.key.on..st	0.00%	3 Missing ⚠️
...sFunctionalTest.class/instance/renderContentOn..st	0.00%	2 Missing ⚠️
...eFunctionalTest.class/instance/renderAnchorsOn..st	0.00%	1 Missing ⚠️
....class/instance/renderCellForDate.row.index.on..st	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1434      +/-   ##
==========================================
- Coverage   49.09%   49.04%   -0.06%     
==========================================
  Files        9144     9143       -1     
  Lines       80565    80552      -13     
==========================================
- Hits        39553    39506      -47     
- Misses      41012    41046      +34     

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[marschall]

LGTM