* feat: now view-variable controls can be registered from content, or even dynamically added
* refactor: whitespaces and xml-doc
* refactor: added changelog entry
* refactor: added methods for adding condition at start and at the end
* refactor: merged start/end methods, for IViewVariableControlFactory, improved changelog message
* refactor: replaced bool insertLast with InsertPosition enum
* refactor: reverse order of checks registration in ViewVariableControlFactory c-tor
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Co-authored-by: pa.pecherskij <pa.pecherskij@interfax.ru>
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