Feature - request inclusion of raw results as well as aggregated summaries in returned object

Please consider including the raw results as well as aggregated results in the value returned by methods such as `FeatureImp$new` - e.g. in lines 312 - 325 of `FeatureImp.R`:

``` r
result <- result[, list(
"importance" = median(importance_raw),
"permutation.error" = median(permutation_error),
"importance.05" = quantile(importance_raw, probs = 0.05),
"importance.95" = quantile(importance_raw, probs = 0.95)
), by = list(feature)]
result <- result[order(result$importance, decreasing = TRUE), ]
# Removes the n column
result <- result[, list(
feature, importance.05, importance, importance.95,
permutation.error
)]
private$finished <- TRUE
self$results <- data.frame(result)
```

It would be nice to add `importance_raw` as a list element either in results or at some higher level of the returned object. That way it allows us to make our own aggregations so we can change the cut off %s, plot the whole distribution, use a different summary statistic (e.g. I note another issue #170 is asking for mean instead of median). And similarly for other methods that return aggregated summaries from some raw initial result.