configure: WARNING: unrecognized options: --with-wepb

It is not needed to follow KVM development blindly and be hit by
bugs during the development.

If provided, shows instance name value in the title, so it is easier to track
and relate shellinabox with a webrunner.

/reviewed-on nexedi/slapos!295

@kazuhiko @arnau This reverts commit bf7c13c6.

/reviewed-on nexedi/slapos!296

This should fix the error below to run zope.

Error: invalid literal for int() with base 10: '10m' (line 39, in file:///srv/slapgrid/slappart7/srv/testnode/awf/inst/test0-7/etc/zope-0.conf)

Make it possible to specify the desired threshold before a requests gets saved to a temporary file instead of being read completely into memory.

@nexedi, tests do pass (I squashed commits) so unless objections today I merge it tomorrow.

https://nexedi.erp5.net/test_result_module/20180216-696E64EA

/reviewed-on nexedi/slapos!290

Current version of wendelin.core is limited in that there's no cooperation
in memory allocation between several processes sharing the same /dev/shm.
Over time, the distribution of memory among processes becomes more and more
inequal until some of them get killed due to allocation failure.

This is a temporary solution that relies on user namespaces.

This moves most of the wrapper recipe to GenericBaseRecipe so that
createWrapper automatically switches to Python scripts for complex cases.

Recipes should not use slapos.recipe.librecipe.execute.generic_exec directly
anymore.

It was used in only 2 places and createPythonScript has no equivalent
(maybe reusing 'initialization' from easy_install would produce something
readable enough). For the moment, let's drop this parameter, so that
createWrapper can switch to Python wrappers for complex cases.

There was an inconsistency between the 2 ways of creating executable wrappers:
- createWrapper: parameters-extra defaults to False
- slapos.recipe.librecipe.execute.generic_exec: no option, enabled

An option for that is not worth the effort.
Let's always enable even if it's meaningless.

/software/ and /stack/ will be cleaned up once a new version of this egg
is released.