allow to use multiple locale directories

remove config options:
- locale_dir
- locale_dir_default

add a config option:
- locale_dirs - a list of directories with locale files (translations)

We start reading locale from the first directory and files with the same name
in each directory are concatenated.

winixd/core/config.h

@@ -592,14 +592,15 @@ public:
 	// default: /usr/local/bin/convert
 	std::wstring convert_cmd;
 
-	// directory with locale files
-	std::wstring locale_dir;
-
-	// directory with default locale files (those from winix)
-	std::wstring locale_dir_default;
+	// directories with locale files
+	// we start reading locale from the first directory
+	// and files with the same name in each directory are concatenated
+	std::vector<std::wstring> locale_dirs;
 
 	// locale files (e.g. "en", "pl")
-	// default: only one item: en
+	// default: "en"
+	// a locale file should define winix_locale_id integer parameter
+	// and it should be smaller or equal to locale_max_id
 	std::vector<std::wstring> locale_files;
 
 	// a maximum value of a locale identifier