port framework_agreement_requisition

minimal work to make the module installable and make the tests pass
update copyright
bump version
improve doc
do not return in __init__
travis: depend on purchase-workflow

This is because framwork_agreement_requisition depends on
framework_agreement which is in purchase_workflow
travis: get server-tools

because framework_agreement needs web_context_tunnel
fix search view
improve doc, move it to README.rst
new field agreement_end_date
popup before generating a framework agreement

This is because the agreement is generated without prices. The wizard
tells the user about that.
rename view file
add fields regarding agreements to the PO
use signal_workflow
translation template
use signal_workflow in the requisition, too
Merge pull request #10 from lepistone/port_framework_agreement_requisition

port framework_agreement_requisition