i18n: use TG2 compatible settings names i18n.lang and i18n.enabled

Following changes are made:
- Remove list of available translations: severely outdated and hard to
  maintain.
- Replace lang with i18n.lang, reasons:
  - Follow TurboGears2 conventions
  - Align with 'i18n.enabled' which cannot be shortened
  - Scoped settings provide grouping and are more clear
  The old 'lang' is still recognized though, so no upgrade issue.
- Introduce/document i18n.enabled

Comments are intentionally kept concise in favor of the documentation.

development.ini

@@ -180,9 +180,13 b' use = egg:kallithea'
 
 full_stack = true
 static_files = true
-## Available Languages:
-## cs de fr hu ja nl_BE pl pt_BR ru sk zh_CN zh_TW
-lang =
+
+## Internationalization (see setup documentation for details)
+## By default, the language requested by the browser is used if available.
+#i18n.enable = false
+## Fallback language, empty for English (valid values are the names of subdirectories in kallithea/i18n):
+i18n.lang =
+
 cache_dir = %(here)s/data
 index_dir = %(here)s/data/index
 

kallithea/lib/paster_commands/template.ini.mako

@@ -181,9 +181,13 b' use = egg:kallithea'
 
 full_stack = true
 static_files = true
-<%text>## Available Languages:</%text>
-<%text>## cs de fr hu ja nl_BE pl pt_BR ru sk zh_CN zh_TW</%text>
-lang =
+
+<%text>## Internationalization (see setup documentation for details)</%text>
+<%text>## By default, the language requested by the browser is used if available.</%text>
+#i18n.enable = false
+<%text>## Fallback language, empty for English (valid values are the names of subdirectories in kallithea/i18n):</%text>
+i18n.lang =
+
 cache_dir = %(here)s/data
 index_dir = %(here)s/data/index
 

kallithea/tests/test.ini

@@ -177,9 +177,13 b' use = egg:kallithea'
 
 full_stack = true
 static_files = true
-## Available Languages:
-## cs de fr hu ja nl_BE pl pt_BR ru sk zh_CN zh_TW
-lang =
+
+## Internationalization (see setup documentation for details)
+## By default, the language requested by the browser is used if available.
+#i18n.enable = false
+## Fallback language, empty for English (valid values are the names of subdirectories in kallithea/i18n):
+i18n.lang =
+
 #cache_dir = %(here)s/data
 cache_dir = %(here)s/../../data/test/cache
 #index_dir = %(here)s/data/index