UsersManual/Index.rst: added Form.showButton
Support: added findInSet()
AbstractBuildForm: added createDeleteUrl(), prepareSubrecord(), getFormTable(). Rewrote buildSubrecord(): added 'delete' link, rearranged 'new' link. 'ShowDebugInfo' enhanced.
BuildFormBootstrap: rewrote BuildButton() to switch New/Delete Button on or off. Show debugInfo as tooltip.
Constants: New Subrecord contants.
formEditor.sql: added Form.showButton. Adjusted records