java-decompiler: fixes and cleanups

- console decompiler: resource closing, lookup instead of scan, error reporting
- logger interface reworked
- saver interface renamed
- bytecode provider returns byte array (to reduce stream leakage)
- extra level of context unit avoided
- unneeded exceptions, dead code, formatting

src/org/jetbrains/java/decompiler/main/extern/IFernflowerPreferences.java

@@ -77,6 +77,7 @@ public interface IFernflowerPreferences {
     put(IDEA_NOT_NULL_ANNOTATION, "1");
     put(LAMBDA_TO_ANONYMOUS_CLASS, "0");
 
+    put(LOG_LEVEL, IFernflowerLogger.Severity.INFO.name());
     put(MAX_PROCESSING_METHOD, "0");
     put(RENAME_ENTITIES, "0");
     put(NEW_LINE_SEPARATOR, (InterpreterUtil.IS_WINDOWS ? "0" : "1"));