Auto tag parent term when child term is selected

Thanks for the suggestion and patch! I'll check it out and if all's well commit it to the dev branch.

Looks like this addresses one of the feature requests in #1728132: Add field instance settings "leaves only" and "select parents automatically".

@#1 Thanks for the patch.
I've tested it

I get the parent term showing up twice
using any hierarchical display setting i.e

hierarchical_term_formatter or hierarchical_select

for example

• London
• London > North London

New patch is attached, based on #1987168-1: Auto tag parent term when child term is selected).

Changes from #1987168-1: Auto tag parent term when child term is selected:

1. the option includes now all the ancestors, not only the direct parents. Basically it is achieved using the function taxonomy_get_parents_all() instead of taxonomy_get_parents(). I think that including all the ancestors has a wider scope, more useful.
2. the ancestors are inserted preserving their hierarchical order. A small processing has been required here.

A sample use case:
Including all the ancestor terms may be very useful for making easier some searches, using filters and/or facets.
e.g:
in a hierarchical vocabulary like:

Europe
        |
        ----- Spain
                      |
                       ------ Madrid

selecting 'Madrid' will include all the 3 terms in the field, preserving the hierarchical order.

#4 works well for me.

Merged to 7.x-1.x, deployed on release 1.0-alpha3. Thanks for the contributions!