Introduced new module "Pages" for HTML-based GUI.
Updated license headers.
Introduced preliminary Tag interface (common for all tags).
Wrote basic code generator and templates for the tags API.
Introduced basic variables (value placeholders) as part of the GUI tree.
Introduced GUI event handlers.
Implemented HTML renderer for the GUI tags tree.
Added generic interceptor-based implementation of the tag interfaces.
Added simple utils with common actions, for simpler GUI construction.
Generated tags interfaces and constructor utils.
Added abstract page skeleton.
Added pager control example.
Fixed HTML escaping in variables.
Improved handlers management in tags.
Implemented basic event handling.
Moved abstract page from "test" to "main".
Removed unnecessary GUI context reference in variables.
Improved naming.
Updated Tags code generation template.
Improved rendering of HTML tags.