- fix "numeric" which was not working at all
 - remove the link to captchas.net
 - ~~partial workaround for the problem that sessions are not shared by zopes~~ dropped, because nexedi/erp5!1451 fixes the root cause 

See merge request nexedi/erp5!1450

This repairs TALES expressions using constructs like `cell is not None` to test if a cell exists, like for example:

https://lab.nexedi.com/nexedi/erp5/blob/1b706b6c29771b5fcbde6499be5df905ca503d5a/bt5/erp5_open_trade/SkinTemplateItem/portal_skins/erp5_open_trade/OpenOrderLine_viewPrice/matrixbox_price.xml#L110


https://lab.nexedi.com/nexedi/erp5/blob/1b706b6c29771b5fcbde6499be5df905ca503d5a/bt5/erp5_pdm/SkinTemplateItem/portal_skins/erp5_pdm/Measure_view/matrixbox_quantity.xml#L110



See merge request nexedi/erp5!1448

This is horrible user experience on mobile, user can accidentally touch the
image and then get redirected to captcha.net website which is generally not
useful. As far as a I understand their conditions of use, they don't require
use to make a link to their website.

It seems this never worked, it was comparing a string received from the client
with a number from the session.

See merge request nexedi/erp5!1452

See merge request nexedi/erp5!1457

we only want to set options to None when not using firefox, but we use firefox
by default. See dicussion on nexedi/erp5@17e1c262 (comment 136933)

See romain/erp5@f10cc273

This requires to rewrite all page content URLs on the fly, to respect the original document baseURI

This improve the HTTP cache usage when browsing multiple web sections.

Attribute must be quoted

also update tests to check if a duplicated supply will not cause doubled price.

See merge request !1445

See merge request !1447

See merge request !1437

TALESValue always had a strange behavior of setting the request as `cell` when
rendering a matrixbox in the case where there was no cell at the given
coordinates, but this code was not used, becase the request was not passed in
kw. When in 777c5e6c ([ERP5Form] Pass request to fields, 2017-12-29) we
changed to always pass the request, this changed the behavior. After this
change when there was no matrix cell, in the TALES context the variable `cell`
became request.

This restore the original behavior (cell being the cell or None), by changing
the questionable code that was not used before.