Changed location of scanned fonts.

In Calibre, there was decided to keep the fonts information inside the
configuration directory. While scanned fonts information is actually a
cache, I would keep it there. This commit is making that happen.

Also removed XMLConfig in favor of JSONConfig class, since XMLConfig is
not used at all.

ebook_converter/utils/fonts/scanner.py

@@ -6,6 +6,7 @@ from ebook_converter import walk
 from ebook_converter.constants_old import DEBUG
 from ebook_converter.constants_old import filesystem_encoding
 from ebook_converter.utils.fonts.metadata import FontMetadata, UnsupportedFont
+from ebook_converter.utils import config
 
 
 class NoFonts(ValueError):
@@ -277,8 +278,7 @@ class FontScanner(Thread):
 
     def reload_cache(self):
         if not hasattr(self, 'cache'):
-            from ebook_converter.utils.config import JSONConfig
-            self.cache = JSONConfig('fonts/scanner_cache')
+            self.cache = config.JSONConfig('ebook-converter-scanner-cache')
         else:
             self.cache.refresh()
         if self.cache.get('version', None) != self.CACHE_VERSION: