Automatically configure boolean attributes for non-XML documents

[malthe]

Boolean attributes are now automatically configured for templates in non-XML mode, presuming that we're being used to generate HTML.

This means that the same loading mechanism can be used for both XML and HTML-based templates.

The list of attributes is defined in chameleon.zpt.template:

BOOLEAN_HTML_ATTRIBUTES = [
    # From http://www.w3.org/TR/xhtml1/#guidelines (C.10)
    "compact",
    "nowrap",
    "ismap",
    "declare",
    "noshade",
    "checked",
    "disabled",
    "readonly",
    "multiple",
    "selected",
    "noresize",
    "defer",
]

See #385 for more context.

[github-actions]

Pull Request Test Coverage Report for Build 6195719017

• 171 of 171 (100.0%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.4%) to 87.422%

---

Files with Coverage Reduction	New Missed Lines	%
src/chameleon/zpt/template.py	1	91.3%

Totals
Change from base Build 6013392085:	0.4%
Covered Lines:	4188
Relevant Lines:	4685

---

💛 - Coveralls

[mcdonc]

I'm going to try to take the tests I wrote to demonstrate the bools-plus-XML issue in #385 and maybe get us a little more coverage on this branch, if it's ok with you.

[malthe]

@mcdonc I took upon me to do this work now, cherry-picking your test cases and fixing some minor expectation issues.

I fixed a minor issue as a result, namely that an XML template (i.e. starting with "<?xml") provided as str did not have its content encoding parsed.

[mcdonc]

Thanks Malthe! nice work

[malthe]

This is now released as 4.2.0.