Add generation of rcheevos hash to DolphinTool

Fixed coding standards issue

CalculateHash return string instead of using char array param

Readme.md

@@ -234,7 +234,7 @@ Options:
                         Path to disc image FILE.
   -a ALGORITHM, --algorithm=ALGORITHM
                         Optional. Compute and print the digest using the
-                        selected algorithm, then exit. [crc32|md5|sha1]
+                        selected algorithm, then exit. [crc32|md5|sha1|rchash]
 ```
 
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