F4901: implement 'delete split files' if primary file is deleted (record) or exchanged against a new one.

F4901: implement split with 'convert' (jpeg). Refactor chmod(), unlink(), rename(), rmdir(), copy() to use by QFQ version which throws an exception.

For updates of QFQ prior to 0.17.0, do:   ALTER TABLE  `Form` COMMENT =  'Version=<your old QFQ version>'
DatabaseUpdate.php, DatabaseUpdateData.php: new class.
QuickFormQuery.php: Add DB UpdateCheck
Database.php: moved to new subdirectory `database`. Add 'ALTER' as a new SQL command.
FormAction.php, TypeAhead.php, Report.php, Sendmail.php, FillStoreForm.php, Store.php, AbstractBuild.php, Delete.php, Evaluate.php: Update path to Database.php.

delete.php, Delete.php: reformat
Link.php: typo

Delete.php: fixed typo.

Delete.php: chdir to the correct directory before starting to delete files

delete.php: extended to support returning JSON, HTML redirect (Location) or HTML error messages.
Report.php: new adjustDeleteParameter()
Delete.php: new.
QuickFormQuery.php: delete() extended to support returning JSON and HTML