Deprecate emulated headlines

Introduce new config option 'emulatedHeadlines', set to false by default,
to deprecate emulated headlines.
The plan is to remove them altogether after two years.

optimise colours for dark templates (via new config option, resolves #97)

changed column toolbar picker to add a whole row of half columns

Attention: This also changed the 'column' lang string from singular to
plural. And it added 'group' to the lists of non-prefixed clas

changed column toolbar picker to add a whole row of half columns

Attention: This also changed the 'column' lang string from singular to
plural. And it added 'group' to the lists of non-prefixed classes.

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added option to set syntax for toolbar picker

allow or disallow certain classes (closes #15)

implemented tabs (re-using them from template styles, closes #12)

added possibility to exclude certain class names from being prefixed with "wrap_" (new config option "noPrefix")

initial release