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/ClassWriter.java

@@ -630,7 +630,7 @@ public class ClassWriter {
           if (isEnum && init) actualParams -= 2;
           if (actualParams != descriptor.params.size()) {
             String message = "Inconsistent generic signature in method " + mt.getName() + " " + mt.getDescriptor();
-            DecompilerContext.getLogger().writeMessage(message, IFernflowerLogger.WARNING);
+            DecompilerContext.getLogger().writeMessage(message, IFernflowerLogger.Severity.WARN);
             descriptor = null;
           }
         }