[CHG] move fields2 and api to openerp root, merge env into api

also fixed a bunch of unrelated import because
[MOVE] openerp.osv.orm to openerp.models

fixup some imports, add a BC shim, back as openerp.osv.orm
[MERGE] remote-tracking branch 'dev/master-apiculture-move-files-xmo' into master-apiculture

Move files around to simplify module structure. Essentially:
    openerp/osv/orm.py -> openerp/models.py
    openerp/osv/fields2.py -> openerp/fields.py
    openerp/osv/api.py -> openerp/api.py