[BUGFIX] Incorrect placement of child elements on paste and localize into flux column

Changed so TYPO3 handles IRRE records in tx_flux_children. Only set tx_flux_parent and tx_flux_column on the copied element in tceMain->cmdmap. Changed tx_flux_parent to a readOnly input so the field is writable according to TCA.

Non solved issues found when testing:
* When moving a localized content element into a flux column, the localized content elements isn't correctly placed.
* When 'Paste in this position' of a localized content element, the localized content elements isn't correctly placed.
* When 'Paste as reference in this position' of a element with child's, the children are also copied.