logging to %appdata% on windows

main/installer-win/pom.xml

@@ -42,7 +42,7 @@
 									<fx:application name="${javafx.application.name}" version="${project.version}" mainClass="${exec.mainClass}" />
 									<fx:info title="${javafx.application.name}" vendor="cryptomator.org" copyright="cryptomator.org" license="MIT" category="Utility" />
 									<fx:platform javafx="2.2+" j2se="8.0" >
-										<fx:property name="logPath" value="cryptomator.log" />
+										<fx:property name="logPath" value="%appdata%/Cryptomator/cryptomator.log" />
 									</fx:platform>
 									<fx:resources>
 										<fx:fileset dir="../target/" includes="Cryptomator-${project.parent.version}.jar" />

main/ui/src/main/java/org/cryptomator/ui/logging/ConfigurableFileAppender.java

@@ -64,6 +64,10 @@ public class ConfigurableFileAppender extends AbstractOutputStreamAppender<FileM
 		} else if (fileName.startsWith("/")) {
 			// absolute Path:
 			filePath = FileSystems.getDefault().getPath(fileName);
+		} else if (SystemUtils.IS_OS_WINDOWS && fileName.startsWith("%appdata%/")) {
+			final String appdata = System.getenv("APPDATA");
+			final Path appdataPath = appdata != null ? FileSystems.getDefault().getPath(appdata) : FileSystems.getDefault().getPath(SystemUtils.USER_HOME);
+			filePath = appdataPath.resolve(fileName.substring(10));
 		} else {
 			// relative Path:
 			try {