Improve Error Handling for UFF Parser

[mstallmo]

The uff parser and functions related to it return booleans in a few locations to indicate success or failure to parse the file. We should convert these boolean values to the Result type in Rust. We should also make sure that the file ends in .uff not only that the location exits.

This should fit nicely into the Result that is already returned when we check to make sure that the path to the .uff file that is passed in to be parsed exists.

[mstallmo]

Closing this since all uff parsing functions that return a boolean for success are implemented returning a result type with custom uff error types.