Draft cdist coding conventions (for types and explorers)

[sideeffect42]

Different types currently use different coding conventions (sometimes even different conventions in the same file).
In the future it would be a plus to have agreed on coding conventions.

Some points that should be included:

• Indentation
• Use of "semicolons" (i.e. where to put then, do, in keywords)
• Guard expected environment variables (e.g. ${__object:?})
• Quotation guidelines

[4nd3r]

my proposal:

• one level is 4 spaces
• use of semicolons should be kept to bare minimum, if \n can be used, then use it
• double quotes when $ is used, with some exceptions (e.g. for foo in $bar), else '
• I have no preference over guarding, but maybe use #!/bin/sh -eu instead? 🦀
• multitest ifs should be split to multiple lines with \\

[4nd3r]

Another thing: file headers?

We have two choices:

1. Enforce copyright (?), license and other info in (almost) every file.
2. Only add # This file is part of cdist. See documentation for more information. when possible.

I feel that second choice is more reasonable. For type's man.rst we already have this information included (e.g. all current and historical authors). There's also LICENSE in repo. Or do we really need to duplicate this to every file at all? What does GPL say about it?

See #5. I removed headers, updated man.rst with all the authors (in alphabetical order) etc. Decided to remove mail addresses, because we shouldn't try to be address book.