The ERPLAB install script should check for write permissions, and report elegantly if requirements not met

[andrewxstewart]

A user reports that the ERPLAB can fail with a nasty error message, even when EEGLAB works fine for them.

An error occurred while initializing child process: While attempting to execute "mv -f "/home/USER/program/eeglab2022.1/plugins/ERPLAB9.00/erplab_Box/erplab_box_readme.md" "/tmp/MATLAB_Files_08-Dec-2022_14_58_47/erplab_box_readme.md"" in context { environment : { ARCH : glnxa64 ....

I suggest checking for write permissions in eegplugin_erplab.m BEFORE doing any writing or moving of files or folders. And then give the user a sensible error message (and perhaps link to a help page on the wiki) if permissions are not met.

I think that specific error is probably due to around line 90 in eegplugin_erplab.m, with erplab_box_readme.md trying to be written without write permission to the EEGLAB+ERPLAB plugin folder.