DOC: More reliable installation instructions

[corneliusroemer]

We should make installation instructions less brittle by configuring the channels permanently.

Setting environment to always use the right channel order:

conda create -n pangolin -y
conda activate pangolin
conda config --add channels defaults
conda config --add channels bioconda
conda config --add channels conda-forge
conda config --set channel_priority strict

For M1 macs, it's necessary to use the osx-64 subdir (bioconda doesn't have arm support yet):

conda activate pangolin
conda config --env --set subdir osx-64

Installation:

conda activate pangolin
conda install pangolin -y

Update:

conda activate pangolin
conda update --all

For a clean reinstall, try:

conda remove pangolin
conda install pangolin

If update doesn't work as expected, remove packages and start fresh.

Remove all

conda activate base
conda remove --all pangolin

I think those instructions should work.

Update: tested install on a fresh environment on linux-64 and arm mac and worked great. It's important that conda-forge is at the top of the channel list if priority is strict. If bioconda comes first, solving fails.