remove perl experimental warnings

use of experimental features would be removed in some future versions
readme reflect the current state of MARC::MIR

as well as some notes on future and the ecosystem.
exemples of validation using kwalify
add mir-dump tool
remove previous test script (useless)
added C4L records repo for the eg/validate demo
fixed link to eg/validate in the doc
path to the ressources fixed in the eg kwalify