Enhanced some example screens.
Fixed Bootstrap theme selection.
Implemented checking for built-in event handlers as a fallback mechanism.
Minor code improvements in generic entity view screen.
Added built-in "cancel" and "back" event handlers.
Replaced custom with built-in "back" and "cancel" event handlers.
Fixed rendering of tag "link".
Added extra attributes specific to the "link" tag (href, rel).
Added support for custom content in the page head section.
Minor refactoring in the generic app page.
Added support for app theme configuration.
Themes menu visibility is hidden when an app theme is configured.
Added attributes specific to the "script" tag (src, language).
Fixed "img" tag rendering (as single tag).
Fixed return type of script tag attribute setters.
Added attributes specific to the "img" tag (src, alt, height, width, usemap).
Added attributes specific to the "script" tag (type, charset, async, defer).
Added attributes specific to the "iframe" tag (src, height, width, seamless, etc.).
Added attributes specific to the "form" tag (action, method, etc.).
Added attributes specific to the "canvas" tag (width, height).