Partly fixes <http://bugs.gnu.org/20255>.
* guix/scripts/package.scm (search-path-environment-variables): Change
'profile' to 'profiles'; expect it to be a list.
(display-search-paths): Likewise.
(%default-options): Remove 'profile' entry.
(%options) <--profile>: Keep previous values associated with 'profile'
in RESULT.
(guix-package)[process-actions, process-query]: Handle the possible
lack of 'profile' pair in OPTS.
* guix/scripts/package.scm (search-path-environment-variables): Add #:kind
parameter. Pass it to 'environment-variable-definition'.
(display-search-paths): Add #:kind parameter and pass it to
'search-path-environment-variables'.
(%options): Add an optional parameter for "--search-paths".
(guix-package)[process-query]: Handle it.
* tests/guix-package-net.sh: Adjust existing test.
* tests/guix-package.sh: Adjust existing tests and add new test.
* doc/guix.texi (Invoking guix package): Document it.
