public void removeCategory(final String cat) {
        if (!categoryCounts.containsKey(cat)) {
            return;
        }
        contentCount -= categoryCounts.get(cat);
        categories.remove(cat);
        categoryCounts.remove(cat);
        invalidateIndexes(null);
    }
A helper class / companion object to help maintaining a list which is divided into categories
<br>
"Categorized lists" mean flat lists where however some entries are category headers and the
following entries are content entries for this category. For example consider following list:
<br>
Colors, Blue, Red, Animals, Cat, Dog, Snake, Fruits, Apple, Orange
<br>
In this list, the entries "Colors", "Animals" and "Fruits" can be considered "category headers"
whereas all other entries are considered "content" (belonging to the category they are placed under)
<br>
For such lists, an instance of {@link CategorizedListHelper} helps with common tasks such as
* maintaining contained categories and their order
* tracks number of actual content entries
* maintains the correct list indexes for category headers
* maps from "list index" to "content index" and vice versa. For example the entry "Red" in above list
  would have a list index of 2 (being in 3rd list position) but a content index of "1" (being the 2nd
  "content entry" in the list)
main/src/main/java/cgeo/geocaching/utils/CategorizedListHelper.java