Added basic config builder

[aluttik]

The readme will still need more work and it wouldn't hurt to add a few more tests for this, but the basics are all there.

usage: crossplane build [-h] [-v] [-d PATH] [-f] [-i NUM | -t] [--no-headers]
                        [--stdout]
                        filename

builds an nginx config from a json payload

positional arguments:
  filename              the file with the config payload

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         verbose output
  -d PATH, --dir PATH   the base directory to build in
  -f, --force           overwrite existing files
  -i NUM, --indent NUM  number of spaces to indent output
  -t, --tabs            indent with tabs instead of spaces
  --no-headers          do not write header to configs
  --stdout              write configs to stdout instead

[dedm]

I would also like to see a test when we

1. parse existing config (A) to a JSON
2. create a config (B) from JSON
3. compare (A) and (B)

[dedm]

NGINX crossplane (branding!)

[aluttik]

haha okay

[gshulegaard]

This is a really clever use of a generator.

[aluttik]

Thanks :)