Allow setting arbitrary package names

[noteflakes]

This is related to #14 (support for non-repository packages). Lyp should allow installing a package under a different name. The format for installing from local path should be extended to allow arbitrary URLs:

# currently works: install from local files
$ lyp install foo@dev:bar

# add this: install from local files without version tag
$ lyp install foo:bar

# also add this: install from URL but rename the package
$ lyp install mypackage://foo.com/bar
# or:
$ lyp install mypackage:https://foo.com/bar