[FIX] #688, partner_relations: creating equal but non-overlapping relations was not allowed

Conflicts:
	partner_relations/model/res_partner_relation_all.py
[ENH] Module partner_relations:
    - Edit relations in pop-up form instead of through inline tree.
[IMP] put one attribute xml elements on one line
Merge pull request #53 from hbrunn/7.0-partner_relations

[IMP] partner_relations: merge from development