First version of RelaxNG validation schema

Covers only change on summary

- Artifacts
- submitted on / submitted by info
- changes on summary

Validate the schema on import

Change-Id: I22104c767d7b1240ec6cc66f2c49274e3a7cee3a
Export TV3 data in xml format

Change-Id: I86feb28a659968c96e457a38d84514ca1d2dc6f9
Add cli script to create tv5 structure from a tv3

Change-Id: I3fed9f137af32d5429d036e1f7e03b2983db4646
Script that migrate a tv3 to tv5

- copy the structure from tv3 to tv5
- export tv3 data in xml format
- import tv3 data into tv5 newly created tracker

Change-Id: I12483c02f48e5455a490f5a19e32ab6e5d32aab9
Import of artifact with only one changeset

Change-Id: I9ee07864c6c039a3ff91ab6ea29a401e86c7bc81
Introduce createNewChangeset at a given date

Change-Id: I2b417cdf9273bce4dbd7ab80ff2e5b4c77137703
Import changesets in the past

Change-Id: Ia5be3056346c636135875412e694a70180334ea9
Merge remote-tracking branch 'gerrit/5828_import_tv3_data_into_tv5' into stable

* gerrit/5828_import_tv3_data_into_tv5:
  Import changesets in the past
  Introduce createNewChangeset at a given date
  Import of artifact with only one changeset
  Script that migrate a tv3 to tv5
  Add cli script to create tv5 structure from a tv3
  Export TV3 data in xml format
  First version of RelaxNG validation schema

Conflicts:
	src/common/autoload.php
This is Tuleap 6.9.99.13

Change-Id: Iaec4f40295a835888f2ec2001c9b507ca52fa6f2