The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue #5074, "pages from other data sources".
But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.
Most notable changes:
* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
This improves the taxonomy template `.Title` situation and make common template constructs much simpler.
See #5074Fixes#5763Fixes#5758Fixes#5090Fixes#5204Fixes#4695Fixes#5607Fixes#5707Fixes#5719Fixes#3113Fixes#5706Fixes#5767Fixes#5723Fixes#5769Fixes#5770Fixes#5771Fixes#5759Fixes#5776Fixes#5777Fixes#5778
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
This commit expands the Resource interface with 3 new methods:
* Name
* Title
* Params
All of these can be set in the Page front matter. `Name` will get its default value from the base filename, and is the value used in the ByPrefix and GetByPrefix lookup methods.
Fixes#4244
Note that this looks like overkill for just the logger, and that is correct,
but this will make sense once we start with the template handling etc.
Updates #2701
Page.GroupByParam function internally uses Page.GetParam to get a
parameter value for a key of a page group but now Page.GetParam returns
a lowercase character string every time. It has no need to using
lowercase character string as a group key value and it confuse a
function user.
This fixes it to keep and return an original parameter string as a group
key value.
Fix#1564
File handling was broken on Windows. This commit contains a revision of the path handling with separation of file paths and urls where needed.
There may be remaining issues and there may be better ways to do this, but it is easier to start that refactoring job with a set of passing tests.
Fixes#687Fixes#660
Following issues are fixed
1. Can't access fields and methods specified in GroupBy call
2. PagesGroup doesn't contain Pages. It's always empty.
3. When GroupBy is called with Section key, it doesn't work as expected
