Reformat onLoad printing

[tsrobinson]

The new auto-setup seems to work great! Now we can think about tidying/consolidating the onLoad printouts. Some suggestions:

• On auto-setup completion, combine set up and loaded messages, i.e. "rMIDAS has been automatically set up and loaded"

  • All other startup conditions, remove "rMIDAS is loaded"

• Simplify and place rMIDAS header prior to messages on configuration -- something like:

"rMIDAS [version] using [CONDA ENV name] (see [internal R call to access custom_python_versions vignette]). For latest updates see https://github.com/MIDASverse/rMIDAS"
"If you use MIDAS, please cite Lall and Robinson (2022) https://doi.org/10.1017/pan.2020.49."

• Delete sentence "Please read https://... your environment."
• Return "If you want to change... configuration" to a new line
• Remove sentence "After resetting..." as this can be printed when reset_rMIDAS_env() is called