CONAN_VERSION is not needed always

[jgsogo]

Main proposals here:

• conan-package-tools is not needed in the base image
• conan is already installed in base image, no need to install it again in deploy ones
• xxxx-conan images are not needed, those are the deploy ones
• CONAN_VERSION is not needed in builder images
• Use explicit CONAN_VERSION in FROM ${DOCKER_USERNAME}/base-ubuntu16.04:${CONAN_VERSION} as deploy

[uilianries]

I would prefer removing Conan from Base and installing only on Conan layer. Once built, we no longer need to rebuild anything, including Deploy, almost Java karma, build once, use everywhere. There is a gap, Clang is missing Conan layer, but it's to fix.

[uilianries]

Amazing job, thank you!