Allow to specify template when running dagger project init

Adds the ability to select a template which will create a new file
in the CWD with the template name. Templates present in the
"cmd/dagger/project/templates" directory are automatically embedded in the dagger
binary when building and then listed in the `dagger project init` help output.

Usage:

    dagger project init -t <template_name>

One idea that we had while pairing on this is to eventually try
improving this UX by extending the `dagger project` command by adding
sub-commands like `dagger project templates [list, new, output, ...]`.

Pair: gerhard

Signed-off-by: Marcos Lilljedahl <marcosnils@gmail.com>

tests/package.json

@@ -4,7 +4,7 @@
     "test": "bats --jobs 4 --print-output-on-failure --verbose-run ."
   },
   "devDependencies": {
-    "bats": "https://github.com/bats-core/bats-core#master",
+    "bats": "https://github.com/bats-core/bats-core#v1.6.0",
     "bats-assert": "https://github.com/bats-core/bats-assert",
     "bats-support": "https://github.com/bats-core/bats-support"
   }