Filter out binary files in folder based projects + untracked git

Untracked git files can often contain binary files (for e.g temp build dir). Similarly, folder based projects can easily have a lot of binary files. Filter such stuff out for these 2 cases. This makes quick open etc nicer to work with and reduces noise with small folder projects.

We can do this for all projects by default too as we are a plain text editor and binary files aren't really useful for kate.