ls: remove the default brown coloring of documents
    
    We leave the list commented out to ease configuration
    for those who want this.
    
    There were two main reasons for removing this default coloring:
    
    1. There are many text file extensions and text files without
    extensions. You couldn't hope to cover them all, and only
    covering a subset introduces inconsistency.
    
    2. Greatly increasing the amount of coloring for these very common
    text files, reduces the "highlighting" effect of coloring in general.