This commit adds support for multiple statDirs both on the global and language level.
A simple `config.toml` example:
```bash
staticDir = ["static1", "static2"]
[languages]
[languages.no]
staticDir = ["staticDir_override", "static_no"]
baseURL = "https://example.no"
languageName = "Norsk"
weight = 1
title = "På norsk"
[languages.en]
staticDir2 = "static_en"
baseURL = "https://example.com"
languageName = "English"
weight = 2
title = "In English"
```
In the above, with no theme used:
the English site will get its static files as a union of "static1", "static2" and "static_en". On file duplicates, the right-most version will win.
the Norwegian site will get its static files as a union of "staticDir_override" and "static_no".
This commit also concludes the Multihost support in #4027.
Fixes#36Closes#4027
Hugo already, in its server mode, support partial rebuilds. To put it simply: If you change `about.md`, only that content page is read and processed, then Hugo does some processing (taxonomies etc.) and the full site is rendered.
This commit covers the rendering part: We now only re-render the pages you work on, i.e. the last n pages you watched in the browser (which obviously also includes the page in the example above).
To be more specific: When you are running the hugo server in watch (aka. livereload) mode, and change a template or a content file, then we do a partial re-rendering of the following:
* The current content page (if it is a content change)
* The home page
* Up to the last 10 pages you visited on the site.
This should in most cases be enough, but if you navigate to something completely different, you may see stale content. Doing an edit will then refresh that page.
Note that this feature is enabled by default. To turn it off, run `hugo server --disableFastRender`.
Fixes#3962
See #1643
