switch sentinel usage to magento registry
remove sentinel model
update layout xml
code should all be using the esi path, still need to update the VCLs
remove ajax specific stuff from vcls
remove ajax helper from ajax template
remove ajax helper references from messages block
fix var usage screwups in _getDefaultEsiOptions
remove ajax references in config
remove references to ajax code path
remove defunct config stuff
add esi method change detection and only set cache flag when caching on esi requests
update changelog
fix typo in changelog
remove ajax helper (again)
fix some rebase issues