nsh env variables expanding
Revert "nsh env variables expanding"

This reverts commit cb7f30317a655f620dfc905069c9066494e99161.
nsh: env variables expansion
nsh: don’t try to expand env variables in nsh_argument
nsh: fixed syntax checking in env variables expanding
nsh: code style fixed
Merge branch 'master' into env_expand
Merge branch 'master' into env_expand
Merge pull request #10 from PX4/env_expand

nsh env variables expanding