docs: add opinionated tile author guide

This guide is for new tile authors to get started or modernize with kiln built tiles.

squashed commits:
- add docs for testing and go import
- add heading for kiln test
- make authoring template parts more useful
- better document the bootstrapping section
- improve documentation for caching compiled releases
- add Stemcell Lock info to commit message
- add shell script command versions
- add curl version for completness
- clairify ominous comment about buildpacks
- document kiln update-release's ability to cause kiln validate to fail
- fix typo
- add documentation on what each kiln release source can do
    this is based on whether the release source implements component.ReleaseUploader
- add local tarballs section
- document kiln glaze
- replace some todos with first draft documentation
- use perm-links for example links