Don't reassess input file type on change

When changing the target path of Input From File (using “…”) don’t silently infer and change the file Type.

Case in point: I have a txt file that I know is a tab-delimited text. If I point EDT to a different filename, it changes the type to Plain Text, thus breaking the import format/column creation.

You can change the expected filetype for an extension in Preferences.

Also more recent versions of Easy Data Transform should be more robust to messing up an input and then changing it back.

I will have a think about how we could handle this better.