Various API clean up, add edit_box locale support, and frame update rate

[cschreib]

• Updated the parent-child documentation in Doxygen and LuaDoc
• Renamed the LuaDoc module "Manager" to "GUI"
• Renamed "frame_strata" and "frame_level" to just "strata" and "level"
• Renamed "blink_period" to "blink_time"
• Renamed "clear_history" to "clear_history_lines"
• Improved consistency of enable/disable functions: for a boolean property X that can be enabled and disabled, there should be enable_X(), disable_X() and set_X_enabled(bool).
• Reduced code duplication with Lua region class names
• Fixed edit_box "OnTextChanged" not always triggered when text is changed.
• Fixed #88
• Changed edit_box "OnCursorChanged" to trigger immediately, and not buffered until update()
• Add vertex_cache_strategy to font_string
• Add update_rate to frame