Add an additional test to "Variant 4, theme, use site base" to also test
for the index.html base (from by testing of #3505). Also add a "name"
field to the test cases to make it easier to know which test is failing
versus just getting a slice index.
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
This commit fixes the base template lookup order to match the behaviour of regular templates.
```
1. <current-path>/<template-name>-baseof.<suffix>, e.g. list-baseof.<suffix>.
2. <current-path>/baseof.<suffix>
3. _default/<template-name>-baseof.<suffix>, e.g. list-baseof.<suffix>.
4. _default/baseof.<suffix>
For each of the steps above, it will first look in the project, then, if theme is set,
in the theme's layouts folder.
```
Fixes#2783
TOML and YAML handles integers differently, creating issues when using integer values from configuration or front matter in the First template function.
This currently works in YAML (parses into int), but not in TOML (parses into int64).
This commit modifies First so it accepts any int.
Fixes#551
The Intersect template-method would fail if one or both of the lists were nil (post vs page; post has tags, page has not).
This commit adds a nil-check and returns an empty result if any of the inputs are nil.
See #537
