change judges interface

Implementation.md

@@ -286,7 +286,7 @@ ReCodEx provides a few initial judges programs. They are mostly adopted from
 CodEx and installed automatically with the worker component. Judging programs
 have to meet some requirements. Basic ones are inspired by standard `diff`
 application -- two mandatory positional parameters which have to be the files
-for comparison and exit code reflecting if the result is correct (0) of wrong
+for comparison and exit code reflecting if the result is correct (0) or wrong
 (1).
 
 This interface lacks support for returning additional data by the judges, for
@@ -300,11 +300,10 @@ implemented:
     - _comparison OK_
 		- exitcode: 0
 		- stdout: there is a single line with a double value which
-		  should be 1.0
+		  should be quality percentage of the judged file
     - _comparison BAD_
 		- exitcode: 1
-		- stdout: there is a single line with a double value which
-		  should be quality percentage of the judged file
+		- stdout: can be empty
 	- _error during execution_
 		- exitcode: 2
 		- stderr: there should be description of error