Support converting a project in place

[dsplaisted]

Usually when converting a project, you want to have it update the project file instead of creating a new one. This especially matters because the assembly name and other properties are inferred from the project name.

I'd suggest that if the -o parameter isn't specified for the convert command, that it simply writes the output to the input file.

I tried specifying that the output file should be the same as the input file, but that gives me a CommandLine.MissingRequiredOptionError.