Enhance target resolving code to cope with more situations

[ged]

handle cases like:

from modules import a as x ... of_kind='x.c.A'

[ged]

It'd be nice to also handle the following case:

in __init__.py:

from a import A
from b import B

setup_all()

in a.py:

    b = ManyToOne('B')

in b.py:

    as_ = OneToMany('A')

Currently this pattern seem to work with python2.4 (that's kind of unexpected), but not python2.5, as reported on the mailing list in thread:

http://groups.google.com/group/sqlelixir/browse_frm/thread/bc8b23a1ae8bd9ec

[ged]

Done in r363, though the pattern described in earlier comment is not supported by default. A global lookup method should work fine for most situations.