[COMMON] New templates to handle repositories

[COMMON] New templates to handle repositories

Current repository templates handles only ONAP "nexus" repository
configuration.
So, all images coming from another repository (currently, OOM is using 4
repository, including nexus one) cannot simply be retrieved from another
one.
This commit add new templates, in a specific chart, in order to change
that.
Now, each for repository can be overidden and all 4 can have a
credentials.

Also, in order to minimize global variables, templates aimed to
retrieve usual utility images (busybox, envsubst, readiness, ...) are
created.

Issue-ID: OOM-2634
Change-Id: I27eb33d830d56ec28f9de68599f5108a262983b3
Signed-off-by: Sylvain Desbureaux <sylvain.desbureaux@orange.com>
[Reduce code size, add missing busyboxRepository]
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>