Allow for string values for filter expressions

[arubb404]

Allow for filtered expressions to contain string values and allow for them to be ANDed or ORed as well. Many components return a string (e.g. Shut or Not Shut), building a filtered expression with a string would allow for the return of only those values and would also allow for not returning value errors from the PI server.

Or if feature already exists, add it to the PIConnect documentation. Current documentation only shows filtering expressions with numbers.

Thank you!