bitbake: cooker: mark setFeatures command as read-only

This patch makes sure that the setFeatures command is marked
as read-only and that it can only run if the cooker is in
the initial state.

Additionally, remove logging from the XMLRPC module in favor
of sending the exception to the client for easy processing.

	[YOCTO #6089]

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
user-manual-metadata.xml: Added new section on mapping functions.

Fixes [YOCTO #5472]
Fixes [YOCTO #1973]

Created a new section called "Automatically Mapping Functions
Within the Context of a Class".  This section addresses the
EXPORT_FUNCTIONS "operator", which was the last of the adjustments
to the variables bug against the BB manual (1973).  The related
bug (5472) is a general bug against enhancing the BB manual, which
this change caps off.

The section here was reviewed and approved by Richard Purdie.

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
world-image: add extra target

* similar to world target, but collects all PACKAGES
* recipes marked with EXCLUDE_FROM_WORLD are excluded from world as well
  as world-image
* recipes marked with EXCLUDE_FROM_WORLD_IMAGE are excluded completely
  from world-image, sometimes you can build 2 recipes in same sysroot,
  but cannot install them in the same image
* PACKAGES listed in EXCLUDE_PACKAGES_FROM_WORLD_IMAGE are also
  excluded. You can remove e.g. ${PN}-dbg, but keep all other PACKAGES.

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>