Implement implode() in a future release

[rotexdegba]

Figure out a unified signature that will work for all kinds of collections.
May not make sense to add as part of CollectionInterface since the operation will vary based on the type of collection you are working with. For example, imploding a collection of integers / strings / floats will be different from imploding a collection of objects / arrays.

A variant implodeColumn($column_name, $glue) could be implemented for ArraysCollection & ObjectsCollection. implodeColumn should implode values from a specified field in each array or object in the collection.