Show a reason when ESL-checked plugin is already an ESL

Previously, we just displayed 'ESL Incapable' without any reason below
the file name when 'Check ESL Qualifications' was run on an ESL-flagged
file. This led to confusion for some users who weren't sure if this was
a bug or expected behavior. We now show 'Already ESL-flagged.' as a
reason, which should make this much more obvious.

Author: Infernio

Mopy/bash/bosh/__init__.py

@@ -2044,7 +2044,10 @@ def _rescanMergeable(self, names, progress, doCBash, return_results):
             if not doCBash and reOblivion.match(fileName.s): continue
             fileInfo = self[fileName]
             # do not mark esls as esl capable
-            if fileInfo.is_esl() or not bush.game.esp.canBash:
+            if fileInfo.is_esl():
+                if return_results: reasons.append(u'Already ESL-flagged.')
+                canMerge = False
+            elif not bush.game.esp.canBash:
                 canMerge = False
             else:
                 try: