Grocery CRUD version 1.5.9

• #420: set_relation with brackets is causing ambiguous column name when the field name exists at the basic table
• #413: Unexpected error when there are non english chars and a datetime field as column
• #406: Export button to work without the need of a popup window or new tab
• Clean-up redundant JavaScript load if it is not required.
• Remove Export as a flash plugin for security reasons and instead add a download link