Merge branch 'ligo-base-image-from-ligo-registry' into 'master'

Use ligo base image from ligo registry instead of dockerhub

See merge request lscsoft/bayeswave!141

.dependencies-el7.Dockerfile

-FROM ligo/base:el7
+FROM containers.ligo.org/docker/base:el7
 
 LABEL name="BayesWave Build Dependencies - EL7" \
       maintainer="James Alexander Clark <james.clark@ligo.org>" \