New Feature: Add depth support to TaggerGetTags

[davidpede]

What does it do?

Adds a new optional depth parameter to TaggerGetTags that adds a search depth for child resources for each parent.

To keep this bc I guess the default should be changed to 1 - I've set it as 10.

Use like:

[[!TaggerGetTags?
    &parents=`1,2,3`
    &depth=`2`
    &rowTpl=`@INLINE <option value="[[+uri]]">[[+tag]]</option>`
]]

Why is it needed?

Currently when using the parents parameter only tags from immediate child resources are returned. This allows fetching tags from deeper down the resource tree.