PI UFL Connector - enable option to treat nulls values for fields as their defined data type instead of as strings

When the UFL connector sends a value that is null, it is treated as a string. As a result, any variables that are defined as other data types (other types as listed here https://docs.osisoft.com/bundle/pi-connector-for-ufl/page/field-section-statements.html) will be sent to PI as a string if the captured value is a null. This can be an issue, especially for tags/AF objects that do not yet exist: when null values are sent by the connector, subsequent values are expected to be of string types as well. If there is a mismatch between subsequent non-null values sent to PI after a null value was the first value sent since connector startup, the value may not be sent successfully and AF object creation may fail or exhibit other undesired behavior. Adding the option to send nulls as their original data type may help mitigate any data flow/AF object creation issues for certain configurations.