Should fix most of the cases where reloading components cause breakage.
There is still a race condition between a transaction's cache being
actually flushed (which can only happen at transaction boundaries) and
another transaction doing the actual class reload, which will
immediately affect all the started transactions in the same process.

Once a portal type class became available again, instances of this classes
should no longer be broken and can be modified again

Some other types (Gadget Type) are currently lacking the interaction workflow
which resets the dynamic classes.

See merge request nexedi/erp5!1243

padding too much in buttom make header bigger, so when export to pdf, header is cut off to hit heigth which make logo display at top

also needs to be declared in hidden content types to prevent adding
directly in preferences

should be same for cases where type based method is a python script, but
is a bit more explicit/safe and consistent with other usages.

In 93e30e5e (Person: Store user id in new user_id property., 2016-12-09)
we adapted this test to the new behavior: title fallback to user_id or
id, but since persons always have a user_id by default, this test was
changed to check that title fallbacks to user_id, but the name of the
test still mention "fallback to id" which became a bit different from
what was tested here.

Revert testEmptyTitleFallbackOnId to check that title fallbacks on id,
using persons without user id and introduce new
testEmptyTitleFallbackOnUserId to describe the new behaviour with user
id.

See merge request nexedi/erp5!1244

See merge request !1241

See merge request !1239

1. title is not exact match
2. can't search title in objectValues