Update rke, kubectl and helm

Update rke, kubectl and helm

This commit updates rke (implementing K8S 1.15.4), kubectl binary and
helm binary with tiller image:

rke             0.3.0
kubernetes      1.15.4
kubectl         1.15.4
helm            2.14.2
dashboard       2.0.0-beta4

Kubernetes dashboard is also updated to be compliant with the 1.15 K8S.

Note 1:
There is a new datalist to split rke only images from other K8S related
images.

Note 2:
El Alto recommendation cannot be fullfilled to the letter, because rke
does not have any release supporting 1.15.2 version of kubernetes (only
experimental).

Issue-ID: OOM-2122

Change-Id: I02cf0955158eca622bcac40ceed42588dbdd3499
Signed-off-by: Tomáš Levora <t.levora@partner.samsung.com>
Signed-off-by: Petr Ospalý <p.ospaly@partner.samsung.com>
Signed-off-by: Bartek Grzybowski <b.grzybowski@partner.samsung.com>