Update timestamp of locationprovider

This adds the possibility to support timestamps with and without milliseconds as well as textual datetime descriptions.
This is needed as different clients use different formats and with this they don't need different parameters.
For example Osmand uses timestamps with milliseconds and GPSLogger uses textual datetime descriptions.
Before Osmand was not working like it was said here:
owncloud-archive#3 (comment)

controller/locationcontroller.php

@@ -44,7 +44,15 @@ public function update() {
 		$params = array('user' => $this -> userId);
 		$location['lat'] = $this->params('lat');
 		$location['lng'] = $this->params('lon');
-		$location['timestamp'] = strtotime($this->params('timestamp'));
+		if(((string)(float)$this->params('timestamp') === $this->params('timestamp'))) {
+			if(strtotime(date('d-m-Y H:i:s',$this->params('timestamp'))) === (int)$this->params('timestamp')) {
+				$location['timestamp'] = (int)$this->params('timestamp');
+			} elseif(strtotime(date('d-m-Y H:i:s',$this->params('timestamp')/1000)) === (int)floor($this->params('timestamp')/1000)) {
+				$location['timestamp'] = (int)floor($this->params('timestamp')/1000);
+			}
+		} else {
+			$location['timestamp'] = strtotime($this->params('timestamp'));
+		}
 		$location['hdop'] = $this->params('hdop');
 		$location['altitude'] = $this->params('altitude');
 		$location['speed'] = $this->params('speed');
@@ -65,15 +73,15 @@ public function addDevice(){
 		$hash = uniqid();
 		$deviceId = $this->locationManager->addDevice($deviceName,$hash,$this->userId);
 		$response = array('id'=> $deviceId,'hash'=>$hash);
-		return new JSONResponse($response);			
+		return new JSONResponse($response);			
 	}
 
 	/**
 	 * @NoAdminRequired
 	 */		
 	public function loadDevices(){
 		$response = $this->locationManager->loadAll($this->userId);
-		return new JSONResponse($response);			
+		return new JSONResponse($response);			
 	}
 	/**
 	 * @NoAdminRequired
@@ -88,15 +96,15 @@ public function loadLocations(){
 		foreach($deviceIds as $device){
 			$response[$device] = $this->locationManager->loadHistory($device,$from,$till,$limit);
 		}
-		return new JSONResponse($response);			
+		return new JSONResponse($response);			
 	}
 	/**
 	 * @NoAdminRequired
 	 */		
 	public function removeDevice(){
 		$deviceId = $this->params('deviceId');
 		$response = $this->locationManager->remove($deviceId,$this->userId);
-		return new JSONResponse($response);			
+		return new JSONResponse($response);			
 	}
 
 }