allow creating modules using specified target names

[vekatze]

Use --target to specify the name of the created target:

neut create foo --target whatever
# Note: Created a module: foo

cd foo

tree
# ./
# ├── build/
# │  └── ...
# ├── source/
# │  └── whatever.nt ← ⭐
# └── module.ens

cat module.ens
# {
#   target {
#     whatever { ← ⭐
#       main "whatever.nt", ← ⭐
#     },
#   },
#   ...
# }