Add debug logging to diagnose iOS stat date issue

iOS helper: log raw stat keys+values for first file to stderr.
IosConnector: already logs stderr at WARN level.
logback.xml: print DEBUG+ for photophetch package to console so
stat output is visible when running ./gradlew run.

src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<configuration>
+  <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>%d{HH:mm:ss} [%-5level] %logger{20} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <root level="WARN">
+    <appender-ref ref="CONSOLE" />
+  </root>
+
+  <logger name="com.bolenpad.photophetch" level="DEBUG" />
+</configuration>