Copy LICENSE when installing an nf-core hosted module

[chasemc]

Briefly discussed in the #modules channel of slack.

"Installing" a nf-core module with
e.g. nf-core modules install . -t untar
doesn't transfer a license, leaving it to the person installing to add a license. It would be nice for nf-core modules install to copy over a license(s) for the installed file(s).

@ewels mentioned:
maybe nf-core modules install should copy the repo license in with the module files..

[chasemc]

Common nf-core template files also have the license manually added to each if they are used within a non nf-core project. Not a big deal to prepend these once, but nf-core sync obviously flags it as different