More Dockerfile updates:  * use Erlang Solutions deb package to get Erlang 18  * use rebar 2.6.0
More Dockerfile updates:
 * use Erlang Solutions deb package to get Erlang 18
 * use rebar 2.6.0

jjhoo/lfe,lfe/lfe,lfe/lfe,jjhoo/lfe,rvirding/lfe,rvirding/lfe