Residual meta data hangs around after changing a project's target language

[cckozie]

I imported a usfm file specifying English demo 1 as the target language. I opened the project chosing multiple source languages, did some work in the project, closed it, and then changed it's target language to English demo 2.
I then imported the same usfm file again specifying English demo 1 as the target language. When I opened this new project it didn't ask me to choose a source text, but opened it using the three I had chosen on the previously imported project, and it scrolled me to the chunk I had last worked on in that previous project.
We should delete any meta data we are saving about the project when it's target language gets changed.