rpopgen docker image needs to be updated with new and development versions

[hlapp]

Several of the packages in the rpopgen Docker image have been (and will continue to be) updated since the last build. As a complicating factor, some of these updates are not yet on CRAN and thus would need to be pulled from Github instead, and some of these introduce backwards-incompatible API changes, in particular for adegenet and hierfstat. Arguably there should be a development version of the Docker image, for which most (or all?) of the packages are pulled from Github instead of CRAN and thus represent upcoming changes on CRAN before they happen there.

This is part of gearing up for publication of the PopgenInfo project (NESCent/popgenInfo#76).

[hlapp]

Also see inquiries to package developers at thibautjombart/adegenet#102 and jgx65/hierfstat#8.

[hlapp]

As a first step, moved hierfstat from installing from CRAN to installing from Github. See v0.2.0.