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
minimal work to make tests pass in v8
autopep8
manual lint
bump version
typo in manifest
adapt tests to changes in the LR module
adapt to changes in models

Specifically, the field logistic_requisition_source_id is not there
anymore.