File and directory structure

Rules for AIP-191, covering file and directory structure.

Rule name	Description
`csharp-namespace`	The `option csharp_namespace` annotation should be idiomatic if set.
`file-layout`	Proto files should follow a consistent layout.
`file-option-consistency`	All proto files must set file packaging options consistently.
`filenames`	Proto files must use reasonable filenames.
`java-multiple-files`	All proto files must set `option java_multiple_files = true`.
`java-outer-classname`	All proto files must set `option java_outer_classname`.
`java-package`	All proto files must set `option java_package`.
`php-namespace`	The `option php_namespace` annotation should be idiomatic if set.
`proto-package`	Proto package must match the directory structure.
`proto-version`	All proto files must use proto3.
`ruby-package`	The `option ruby_package` annotation should be idiomatic if set.

Note: Because AIPs sometimes cover topics that have some overlap, some rules related to file and directory structure may be included in the rules for other AIPs.