bin/bitbake: Improve exception handling

Due to the internal event processing, this excepting handler usually raises an
Empty error, masking the underlying failure. Ensure the original exception is
raised.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
bitbake: Create cookerdata splitting config from cooker and bin/bitbake

Currently the UI and server configuration is one big incestuous mess. To
start to untangle this we creater cookerdata, a new module which contains
various confiuration modules and the code for building the base datastore.

To start with we add a ConfigParameters() class which contains information
about both the commandline configuration and the original environment.

The CookerConfiguration class is created to contain the cooker.configuration
options. This means we can transfer new paramters to the server over something
like XMLRPC and then build a new configuration from these on the server.

Based on a patch from Alexandru Damian <alexandru.damian@intel.com>

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Move commandline parsing back into the UI/cookerdata

Building up a set of actions for the server is tricky since we depend upon the
commandline but fall back to values from the datastore. We should be able to build
a datastore without a commandline and vice versa. Ultimately the UI should send
the commands to the server.

This patch amounts to code rearranging, moving the heavy lifting to the UI, though
a helper in the configuration option. This will need further cleanup/tweaking but
this should be the only update needed to the UIs. The code now queries the server
for any missing data should it need to.

This code allows various knowledge of configuration variables to move to the UI side
only, partcularly pkgs_to_build but also all the command specifiers. It should also
be possible to move cmd eventually, I'm just unsure if any callers call the commands
expecting this to default to something sane right now.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
cooker: Split configuration parsing code into cookerdata

In order to have a memory resident bitbake and to allow task execution, we need
to be able to rebuild the base configuration without a cooker. This moves the
code into its own class so it can be built independently.

The interface is less than ideal here but I didn't want to add parsing methods
a subclassed DataSmart, at least until we've experimented further with this code
and are certain that makes sense. At the very least, the methods are ugly and need
cleaning up.  Spliting the code out seems to be the right thing to do though and
should unblock various activities on BitBake so I believe this code is a step in
the right direction.

Based on a patch from Alexandru Damian <alexandru.damian@intel.com>

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
bitbake/cookerdata: Explicitly specify cooker configuration options

As the code stands today its hard to know which configuration variables
are used by which parts of the system. Some are used by the UIs, some
by bin/bitbake itself, some by cooker.

This patch changes the configuration to just contain the variables cooker
uses, and changes bin/bitbake to access the variables it needs directly
which hopefully lets us start to untangle this mess.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>