Implemented loading VC from gz files & updated OAuth2 expiry check.

Change-Id: I01c607b86b992526400a3df9c5a66fa6211f4ac8
diff --git a/core/pom.xml b/core/pom.xml
index 01dbacd..7f9e282 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -203,8 +203,18 @@
 		    <groupId>org.apache.logging.log4j</groupId>
 		    <artifactId>log4j-jul</artifactId>
 		    <version>2.11.0</version>
+		    <exclusions>
+		    	<exclusion>
+					<groupId>org.slf4j</groupId>
+					<artifactId>slf4j-api</artifactId>
+				</exclusion>
+		    </exclusions>
 		</dependency>
-		
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-api</artifactId>
+		    <version>1.7.25</version>
+		</dependency>
 		<dependency>
 			<groupId>junit</groupId>
 			<artifactId>junit</artifactId>
@@ -283,6 +293,10 @@
 				</exclusion>
 				<exclusion>
 					<groupId>org.slf4j</groupId>
+					<artifactId>slf4j-api</artifactId>
+				</exclusion>
+				<exclusion>
+					<groupId>org.slf4j</groupId>
 					<artifactId>slf4j-log4j12</artifactId>
 				</exclusion>
 				<exclusion>