add version migration of sabredav from 1.8.1 to 4.0.3 and updated files where it is used

composer.json

@@ -431,7 +431,7 @@
 		}
 	],
 	"require": {
-		"php": ">=5.6.40",
+		"php": ">=7.0.0",
 
 		"afarkas/html5shiv": "3.7.*",
 		"alvaro-prieto/colresizable": "1.6",
@@ -492,7 +492,8 @@
 
 		"rmariuzzo/jquery-checkboxes": "1.0.7",
 
-		"sabre/dav": "1.8.10",
+		"sabre/dav": "4.0.3",
+		"sabre/event": "5.0.3",
 		"scottjehl/respond": "1.4.2",
 
 		"tapmodo/jcrop": "2.0.4",