A zindex of -1 breaks handsontable.

This reverts commit 514a5157.

This is very convenient when we use portal_templates.upgradeSite to
make sure some bt will always be installed with force=1. This is
usually used when we have a bt patching other bt.

Allows implementing user-based restrictions on classical ERP5-style
rendering.

This functional change should have been in a separate commit.

Commit accidentally reverted "IE use the latest rendering engine to
render the page". Reapply the change.

That template is only to be used for ERP5-style UI.

That template is only to be used for ERP5-style UI.

To encourage creation of alternative templates for web mode,
as this template must not be used outside of ERP5-style UI
(aka "ERP5 XHTML Style").

Sadly, we still implement our own escaping, as places escaping strings do
not know which connector will be used (proper escaping is
connector-dependent, because database-dependent).
Move this method in ZSQLCatalog to factorise code.

Disabled by default (configurable by user preference).

Also, reorganise erp5_auto_logout code:
- logout: Do not duplicate original code.
- twiddleAuthCookie: Simplify & factorise.
- setAuthCookie: Resync features with Cookie Crumbler's, and set http_only flag.
- ERP5Site_getMaxUserInactivityDuration: Cached access takes the same time as actual access (and access is surprisingly slow, actually), so do not cache.
- Base_getAutoLogoutSessionKey: New script, to factorise session key generation.

Editor Field does not escapes value, String Field does.

also :
* remove Accept-Encoding from Vary header, because Zope's response does not differ by Accept-Encoding request header.
* use getModificationDate() for modification time if available.

Editing a text containing </textarea> was breaking the field