fix: errors are logged not echoed

Test plan:
    - navigate to Aspen Administration > EBSCO EDS >
    Settings
    - create a new Setting, make sure to use invalid
    credentials and save
    - navigate to Aspen Administration > Primary
    Configuration > Library Systems and select your
    current Library
    - set its EDS Setting to the setting you just
    created
    - log out
    - run a search in Articles and Databases

Before this commit:
An error message appears at the top of the screen.
This message contains the information sent back by
EDS.

After this commit:
The error message does not show on screen anymore
and is logged instead.

code/web/sys/SearchObject/EbscoEdsSearcher.php

@@ -126,6 +126,7 @@ public function getCurlConnection() {
 	}
 
 	public function authenticate() {
+		global $logger;
 		if (SearchObject_EbscoEdsSearcher::$authenticationToken == null) {
 			global $library;
 			$settings = $this->getSettings();
@@ -185,12 +186,12 @@ public function authenticate() {
 							//echo("Authenticated in EDS!");
 							return true;
 						} elseif ($createSessionResponse->ErrorDescription) {
-							echo("create session failed, " . print_r($createSessionResponse));
+							$logger->log("create session failed, " . print_r($createSessionResponse, true), Logger::LOG_WARNING);
 							return new AspenError("Error processing search in EBSCO EDS");
 						}
 					}
 				} else {
-					echo("Authentication failed!, $return");
+					$logger->log("Error processing search in EBSCO EDS: " . print_r($return, true), Logger::LOG_WARNING);
 					return new AspenError("Error processing search in EBSCO EDS: Authentication failed");
 				}
 			} else {