WebComment: general comment format improvements

* Introduces the CFG_WEBCOMMENT_ENABLE_HTML_EMAILS config variable.
  When True, emails will also include HTML content.

* Introduces the body_format column for cmtRECORDCOMMENT that describes
  the format of the body of each comment ("HTML", "TEXT", etc.).

* Handles comments appropriately when storing and displaying them,
  according to their body format and desired output format. (closes #2064)

Co-Authored-By: Nikolaos Kasioumis <nikolaos.kasioumis@cern.ch>
Signed-off-by: Nikolaos Kasioumis <nikolaos.kasioumis@cern.ch>
1: D290 White spaces around docstring should be trimmed.
1: D400 First line should end with '.', not 'e'
4: I102 copyright year is outdated, expected 2014 but got 2011
28:1: E302 expected 2 blank lines, found 1
28: D401 First line should be imperative: 'Take', not 'Takes'
28: D202 No blank lines allowed *after* function docstring, found 1
28: D400 First line should end with '.', not ':'
28: D205 Blank line missing between one-line summary and description
183:1: E302 expected 2 blank lines, found 1
183: D401 First line should be imperative: 'Take', not 'Takes'
183: D202 No blank lines allowed *after* function docstring, found 1
183: D400 First line should end with '.', not ':'
183: D205 Blank line missing between one-line summary and description
213:8: E225 missing whitespace around operator
227:1: E302 expected 2 blank lines, found 1
227: D202 No blank lines allowed *after* function docstring, found 1
227: D205 Blank line missing between one-line summary and description