- show the situation that packages succeeded to build, but are not yet published (way to many questions due to that)
- do not show unpublished information in dirty situation
- update NEWS file
- reworked the plugin loading mechanism

Using the "old" exec approach isn't possible anymore because it'll break all
plugins which aren't compatible with python3 (for instance the usage of
python2's "print" statement will lead to an error). In order to circumvent
this problem we do the following:

- import the plugin/module
- update the module's global symbol table with the "globals()" of the
  commandline module
- bind the module's "do_*" functions to the "Osc" class

This basically mimics the old "exec" semantics.
- removed plugin migration hint from the NEWS file (for now)
- mention reworked plugin loading mechanism in the NEWS file

Also added information about a potential problem and how to
fix it (if a plugin uses the "@cmdln.option(...)" decorator it can't be
loaded/imported)
- oscssl.verify_certificate: also print cert info if http_debug is set

If http_debug is set we redirect sys.stdout to an StringIO
instance in order to do some header filtering (see conf module)
so we have to use the "original" stdout for printing the certificate
information.
Catch specific exception. Catch-all is calling for error
Display meaningful message for queries w/o project

Like: osc rq list -U $USER -t change_devel
- small fix for commit d338254bb7ee260e2be96d2345547c59adfa83ad

catch HTTPError instead of TypeError