Was causing things like emjoi within script content to be somewhat
mangled. Instead we force UTF8 only parsing via XML declaration.
Added test to cover.
For #2923
Fixes a strange issue of HTML tags within script tags being malformed
when part of the HTML custom head content due to the PHP parsing we do.
DOMDocument seemed to cause this upon load.
Adding LIBXML_SCHEMA_CREATE to the ->loadHTML call seems to fix this but
not really sure why. Doesn't seem to cause further issues though.
Tested with multiple scripts and styles and comments and meta tags.
- Also added new testing class to cover.
- As part of testing, added new folder within tests to house setting
specific tests.
For #2914
In particular, That around the casing of dangerous values within
attributes. This uses some xpath translation to handle different casing
in contains searching.
Fixes issues thrown in custom HMTL head & page content filtering when
the content is comprised of only a single HTML comment.
Adds tests to cover.
For #2804
