Bug 25700: Complete KohaCons informations in timeline

Bug 25700: Complete KohaCons informations in timeline

Last entry for KohaCons on Koha timeline was for 2013.
This patch :
- adds KohaCons from 2014 to 2020
- adds missing link to KohaCons websites for events from 2006 to 2013
- suppresses dead links for old KohaCons
- standardizes the display of informations

To test, apply patch and check :
- there is no typo (especially for October > Octobre)
- order of dates is correct
- links to Koha website ou wiki are correct

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>