Support for Apptainer

[pojeda]

For Apptainer this worked in my case, assuming one has a soft link "singularity" that points to the Apptainer installation, otherwise one would need to change "singularity" strings to "apptainer" in the code:

apptainer pull docker://conglab/dpam:latest

git clone https://github.com/CongLabCode/DPAM
cd DPAM/
wget --no-check-certificate https://conglab.swmed.edu/DPAM/databases.tar.gz
tar -xzf databases.tar.gz # Your project will need more than 800 GB

In the file run_dpam_singularity.py, delete only the string "--fakeroot" (on line 75), which could create issues, for instance, with GLIB