Made invoice optional from store config checkbox, updated and regen database script, few config fixes (#410)

database/database.sql

@@ -23,11 +23,8 @@ INSERT INTO `ospos_app_config` (`key`, `value`) VALUES
 ('return_policy', 'Test'),
 ('timezone', 'America/New_York'),
 ('website', ''),
-('recv_invoice_format', '$CO'),
-('sales_invoice_format', '$CO'),
-('tax_included', '0'),
-('invoice_default_comments', 'This is a default comment'),
 ('company_logo', ''),
+('tax_included', '0'),
 ('barcode_content', 'id'),
 ('barcode_type', 'Code39'),
 ('barcode_width', '250'),
@@ -46,8 +43,12 @@ INSERT INTO `ospos_app_config` (`key`, `value`) VALUES
 ('receipt_show_total_discount', '1'),
 ('receipt_show_description', '1'),
 ('receipt_show_serialnumber', '1'),
+('invoice_enable', '1'),
 ('use_invoice_template', '1'),
+('recv_invoice_format', '$CO'),
+('sales_invoice_format', '$CO'),
 ('invoice_email_message', 'Dear $CU, In attachment the receipt for sale $INV'),
+('invoice_default_comments', 'This is a default comment'),
 ('print_silently', '1'),
 ('print_header', '0'),
 ('print_footer', '0'),