remove existing tests: they are now irrelevant

I discussed this with @yvaucher and @rdeheele. These tests are long
flows taken from logistic_requisition before logistic_budget was split
out, that check functionality of logistic_budget that is not there
anymore (we removed the old constraints). We did not notice the problem
because the only assertion was disabled to work around a bug in the
core, recently fixed.

For the new functionality I will not recover these tests, as they are
not really relevant here, and add new ones, more isolated.
bump
add budget to CE and propagate it from LR
show total budget on the view, over_budget check
test: not over budget
new integration test: it can block
test: it can pass
set budget per line, compute on the order
store the total budget
make mock stricter with spec_set

That way I can read and write only attributes of the real logistic
source.
refactor budget_amount -> budget_tot_price

So that it is consistent with the same field on the logistic request.
Make a test stricter to drive this change.
check it has no budget holder
test has budget holder
configure no budget holder exception
logistic_requisition tests: no sale exceptions

If some module enables sale exceptions (like logistic_budget), the
integration tests of logistic_requisition will fail. Disable the check
in the tests, because it is irrelevant to the module.
add propagation of approval data to cost estimate
show budget in line
update readme
lint
remove useless assertion