Improve test coverage and fix issue in path loading (#602)

* reactivate skipped tests

* remove unused internal interfaces

* enable pytest in VS Code

* simplify and fix path logic in loader

* increase test coverage

* test missing config

* check for wrong printer names

* Skipped appdir test

src/escpos/codepages.py

@@ -12,10 +12,6 @@ class CodePageManager:
         """Initialize codepage manager."""
         self.data = data
 
-    def get_all(self):
-        """Get list of all codepages."""
-        return self.data.values()
-
     @staticmethod
     def get_encoding_name(encoding):
         """Get encoding name.