Refactor parsing of pattern parameters.
Refactor parsing of pattern parameters.

Quoting of values is no longer supported. This did not work in any
useful way, so no functionality is lost. Sites relying on quoting
will need to update their markup.

Fix handling of parameter values containing an equal-sign. Previously
values were chopped off at the first equal sign, so a parameter suchas
```param=value=morevalue``` would result in the value being seen as
```value``` instead of ```value=morevalue```.

Patternslib/require-experimental-build,Patternslib/Patterns-archive,Patternslib/Patterns-archive,Patternslib/Patterns-archive