lisa.datautils: Add a "lisa" custom namespace for Series and DataFrame
lisa.datautils: Add a "lisa" custom namespace for Series and DataFrame

Functions in datautils will now be available like this:

    # Calling the function of datautils directly
    x = df_foobar(df, ...)

    # Using the "lisa" namespace registered on pandas.
    # note: the function has its "df_" or "series_" prefix removed.
    x = df.lisa.foobar(...)

ARM-software/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,credp/lisa,credp/lisa,ARM-software/lisa