Changed order-lab-tests mapping to fpml

[kozlovana]

Questionnaire with title 'Add Laboratory test results' can be created both from Encounter and from Documents tabs.

[ir4y]

[kozlovana]

@ir4y You’re right, this doesn’t work because I referenced the wrong questionnaire in description.
I mistakenly mentioned 'Add Laboratory test results' in the description, while the correct questionnaire for this PR is 'Order laboratory tests' (id: order-lab-tests).

The 'Order laboratory tests' questionnaire with new mapping correctly creates resources both from the Encounter and Documents tabs in my local environment.

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As for 'Add Laboratory test results', we already discussed the problem here: #611

[ir4y]

@kozlovana Now empty encounter is always passes to Patient Document.
Please fix the reported error.