Make sure when 'sign' definition is added via vimside#sign#AddCategory
that the data has an 'ids' entry.
Made sure that when a 'sign' Clear function is called that the associate
id is removed from the 'ids' Dictionary.
There is now an Option, 'sign-start-place-id' with default value 2656
which is the value of the first 'sign' id. Subsequent ids are one greater
than there predecessor.