Reorganize ecosystem page

[danielfernandez]

Right now the ecosystem page is a bit of a mess:

• The Conditional Comments dialect should be removed, as it is no longer needed in 3.0
• The Tiles dialect should be removed temporarily, waiting for the future existence of a Tiles 3 one.
• Many community dialects and extensions are not updated to / compatible with 3.0
• Some community dialects and extensions seem simply abandoned.
• We should get rid of the Demos section, update the SQL dialect to 3.0 and list it elsewhere.
• Some style changes should help the readability of the page, which right now is not ideal.

[ultraq]

Agree, it is in need of some love and updating!