Collective.vdexvocabulary

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- added **History**, **How to access relations (from code)** and **Example
VDEX file** section to README.
[garbas]

- moved code to http://github.com/collective/collective.vdexvocabulary.
[garbas]

- BUG(Fixed): when vdex file was loaded it failed if there were not terms.
[garbas]

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- add documentation and clean up code a little bit.
[garbas]

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- initial release.
[garbas]