This extends the page grouping in Hugo with a template function that allows for ad-hoc grouping.
A made-up example:
```
{{ $cool := where .Site.RegularPages "Params.cool" true | group "cool" }}
{{ $blue := where .Site.RegularPages "Params.blue" true | group "blue" }}
{{ $paginator := .Paginate (slice $cool $blue) }}
```
Closes#4865
common/errors/errors.go:21:1: comment on exported var FeatureNotAvailableErr should be of the form "FeatureNotAvailableErr ..."
common/errors/errors.go:23:5: error var FeatureNotAvailableErr should have name of the form ErrFoo
common/maps/scratch.go:76:1: comment on exported method Scratch.Delete should be of the form "Delete ..."
common/maps/scratch.go:133:1: exported function NewScratch should have comment or be unexported
common/types/types.go:44:1: exported function NewKeyValuesStrings should have comment or be unexported
A sample config:
```toml
defaultContentLanguage = "en"
defaultContentLanguageInSubdir = true
[Languages]
[Languages.en]
weight = 10
title = "In English"
languageName = "English"
contentDir = "content/english"
[Languages.nn]
weight = 20
title = "På Norsk"
languageName = "Norsk"
contentDir = "content/norwegian"
```
The value of `contentDir` can be any valid path, even absolute path references. The only restriction is that the content dirs cannot overlap.
The content files will be assigned a language by
1. The placement: `content/norwegian/post/my-post.md` will be read as Norwegian content.
2. The filename: `content/english/post/my-post.nn.md` will be read as Norwegian even if it lives in the English content folder.
The content directories will be merged into a big virtual filesystem with one simple rule: The most specific language file will win.
This means that if both `content/norwegian/post/my-post.md` and `content/english/post/my-post.nn.md` exists, they will be considered duplicates and the version inside `content/norwegian` will win.
Note that translations will be automatically assigned by Hugo by the content file's relative placement, so `content/norwegian/post/my-post.md` will be a translation of `content/english/post/my-post.md`.
If this does not work for you, you can connect the translations together by setting a `translationKey` in the content files' front matter.
Fixes#4523Fixes#4552Fixes#4553
This closes#98, even if this commit does not do full content text search.
We may revisit that problem in the future, but that deserves its own issue.
Fixes#98
