Fix missing space before 'width'

The newly introduced width-param on figure did not work in combo with alt or caption due to space-issues.

This fixes that.
Allow partial without .html

`partial "header" .` means the same thing as `partial "header.html" .`.
Fix a bug with taxonomy rendering.

- In `layouts/_default/taxonomy.html`, the `.Data` result does not
  provide the same information that `layouts/_default/terms.html` does
  for being able to identify the plural value of the term.
- This change adds `.Data.Singular` and `.Data.Plural` to provide
  similar capabilities.
- This *may* be incompatible with templates that check for `{{ if ne
  $taxonomy "Pages" }}` if the `page.Params` has either the singular or
  plural values as keys.
Add Git directory deployment flow to tutorial
Added better error message for poorly formed frontmatters in archtypes
Params map has string as key

Related to issue #540 and commit 3c22ca7c84456b19f2a017719b1533902594e672
Make Where template-method accept methodname as key

This is necessary to make constructs like `{{ range first 1 (where .Data.Pages "Type" "post") }}` -- as Type and Section is methods not fields.