"Custom vs Standard" paths reviewed.

json-c and rdkafka management now better taken into account.
This allows compiling on a ubuntu server as weel as on a centos distribution.

Change-Id: I1c8adf8ab213c2a7d4927fbbe1e031dc782792ea
metautils : recent headers now installed too

Change-Id: I241699ae0ecd8f68be28386b0659f2cd6068e66d
Merge "metautils : recent headers now installed too"
sqlx_service: an URL can now be announced, different from bind URL

In addition, checks have been added on the URL provided.

Change-Id: Ib21f8d07c2224385df2c515fc43a22e0cd5a415c
Merge "sqlx_service: an URL can now be announced, different from bind URL"