profile: display copy-paste-able instructions on installing reana-client

[tiborsimko]

Different versions of REANA cluster are to be used with different versions of REANA client.

Currently, newer versions of reana-client are not guaranteed to support past versions of REANA client.

It would be good to enrich e.g. Your profile web page:

to also display information about which reana-client version to install. For example:

$ virtualenv ~/.virtualenvs/reana
$ source ~/.virtualenvs/reana/bin/activate
$ pip install 'reana-client>=0.6,<0.7'

... or pip install reana-client==0.7.0a3 or whatever admins will decide. So this should be configurable e.g. via Helm.

P.S. Let's also check the instructions displayed on the welcome page for non-CERN installations... It could do the same.

P.S. This can go into maint-0.7 since it may be considered a bug fix of sorts.