Doc: Improve SQL Example: Cached Table Example

• Revert button in the example application could be more intuitive, as it is available after a 'Submit' but does not revert submitted changes.
• The table layout does not fill the default application size, which makes it look a little unpolished.
• Wrong order of arguments in description of TableEditor constructor.
• The text "class can be used to provide data to view classes" is ambiguous: are we using 'view' as noun or verb? (It is used as noun, but reads as a verb).
• Overall language can be simplified somewhat, to make the text clearer for non-native English readers.
• "It is build" -> "It is built".
• Sub-section "Connecting to a Database" is enclosed in a table - the formatting makes it look like a sidebar, although the text seems to be a continuation of the main text. Is this done on purpose?
• The text content that goes into the 'items' table in the database is marketing speech (or an attempt at clever SEO trickery). It feels a little contrived. Perhaps rename the table to 'slogans', 'marketing_pitches', or something similar that justifies the content? Or replace content with something that is more benign.
• The text mixes active/passive voice as well as point of view (first person vs second person).
• Use of possessives, Latin expressions: rewrite to improve readability for non-native English readers.

See also:

• https://wiki.qt.io/Examples_Revamping_Qt_SQL#Notes
• https://wiki.qt.io/Examples_Revamping_Qt_SQL#Examples