Remove index value for existing object #81
Description
Let $object be \Riak\Object. It is easy to add new values to be indexed via secodary index (available for leveldb):
$object->addIndex($indexName, $indexValue);
When the $object already have some index values, it is also possible to read them, such as:
$indexMap = $object->getIndexMap();
However, there is no option to remove an existing index. This would be particularly useful when updating an existing record (re-writing $object retrieved via $object = $riakEntity->getFirstObject();). If I need to remove an existing index, I need to create a new Riak\Object and copy all values. It would be nice to have a method to remove an existing index, such as:
$object->removeIndex($indexName);