Remove pg-post-tasks and add common bash variable and functions

[cat-bro]

Remove time-consuming pg-post-tasks role and put its tasks into the common role in a more efficient form. If there are environment variables which need to be the same for all users, these can be set in one common file.

Add bash functions for all users jwd, go-jwd and others. We can add more of these and ones that are helpful on pulsar VMS, useful aliases etc over time.

Add a variable skip_machine_users that can be set to true to skip all of the user loop tasks in the common role. I'd like to add this to the Makefile: maybe make run galaxy --skip_users or make skip-users galaxy to run a playbook without the user tasks.

[cat-bro]

Hi @jlqfab, we can add other common bash variables here as well like export EDITOR=vim. This is not ready for merge because I'd like to add a few more things such as a jwd function for pulsar

[jlqfab]

This looks good!

[jlqfab]

@cat-bro besides the EDITOR export, I like to change the defaults in the .bashrc for HISTSIZE and HISTFILESIZE, so that history doesn't get erased too quickly (1000 lines of history is exceeded very quickly).