* more locale fixes:
- fix running wb-manager w/o i18n dependencies
- dependencies: move babel to extra_requires, show warning if locale used or 'wb-manager i18n' called and i18n are not installed
- not found page: don't language switch header banner on nested content frame
* localization / doc fixes:
- add missing header.html
- docs: support 'i18n' extra, mention in docs
- use 'default_locale' for html lang tag
- access control docs: fix documentation for adding user with acl command
* localization: add compile_catalog after extract as well to simplify updates for identity (en) locale
* ui:
- include locale in home page collection listing
- keep locale on error page home link
* autoescape:
- ensure jinja2 templates are autoescaped to prevent xss issues (thanks @sebastian-nagel for suggested fix)
- ensure banner inserts are not double-escaped
- update tests for template autoescaping
* update CHANGES.rst
* bump version to 2.6.0b1
