GLOBAL : allow fetching version of each component of Cytomine

[geektortoise]

In this PR (cytomine/Cytomine-Web-UI#108), we allow to display the version of each component. The version is encoded in the configuration of the front-end.
It would be better that the FE fetch the version of each component ? This implies that main component (with an API) can return the version of theirselves and of their dependencies (core -> postgres)

I think the definition of the version inside some variables in the bootstrap that can automatically update the FE configuration will only work for a deploiement on the same VM.