Externals Update, master branch (2019.06.07.)

Updated all projects to use atlasexternals-2.0.30. It has just one update wrt. the currently used atlasexternals-2.0.29 tag. (atlasexternals@2.0.29...2.0.30) It fixes a bug that was introduced recently in how the CINT dictionary generation code figures out when it should re-generate the dictionary source file.

That issue was discovered in !23831 (merged), and discussed a bit in ATLINFR-1644.

At the same time I also updated VP1Light to use the same version of atlasexternals that all the other projects use. @rbianchi, I assume this would be okay, right? All the VP1 related updates have been in the master branch of the externals repository for a while now, right?