properties using other properties

[cpb <cpb@snotbubble.com>]

Is there a way to set properties using other properties?  Doesn't matter
if its on export only, though it would be nice to have it in-situ.

here's an example (obviously doesn't work), where a project properties
for the project client only needs the CLIENT property filled, the rest
of it automatically populates on export.  Would save having to duplicate
the data where there are a lot of projects.


* client1
    :PROPERTIES:
    :CUSTOM_ID:        client1
    :NAME:             a client
    :ADDRESS:          an address
    :EMAIL:            an email
    :URL:              a website
    :END:

* project1
    :PROPERTIES:
    :CUSTOM_ID:        project1
    :NAME:             a project
    :CLIENT:           client1
    :CLIENT_NAME:      {{{property(NAME,#{{{property(CLIENT)}}})}}}
    :CLIENT_ADDRESS:   {{{property(ADDRESS,#{{{property(CLIENT)}}})}}}
    :CLIENT_EMAIL:     {{{property(EMAIL,#{{{property(CLIENT)}}})}}}
    :EXPORT_FILE_NAME: ./a_project
    :END:

    project....: {{{property(NAME)}}}
    for........: {{{property(CLIENT)}}}
                 {{{property(CLIENT_ADDRESS)}}}
                 {{{property(CLIENT_EMAIL)}}}