Add preference of encounter provider under setting

Majority of time, the provider is the one who actually fills out the encounter form on mUzima. It would make sense to have a setting to allow the user to have the preferred setting as logged-in user as the encounter provider. However, there might be small number of cases which are exemption.

By adding the option under setting would allow users to decide whether they want to have it by default (logged in users as encounter provider) or not.

As a provider on the device side, I want to set myself as the defaulted encounter provider so that I don't need to update such info when filling out form templates.

Acceptance Criteria:
Login user is set as provider for all form templates. If user doesn't want himself/herself to be set as provider, he/she can uncheck the option under Setting.