Letting users define custom global functions that persist, and local functions that are accessible to flow scripts in the same folder

[kensoh]

In current version of TagUI, if custom functions are defined by users, they would be defined as part of the automation flow or subscripts to be called via tagui step. If custom functions are defined in tagui_header.js, they would be overwritten when there is a new release of TagUI.

This issue aims to add support for letting users create a tagui_global.js file in tagui/src folder, which they can define global helper functions for use in their automation scripts. And this tagui_global.js persists with newer TagUI releases as there isn't a tagui_global.js file as part of the repo.

[kensoh]

This feature is now usable from the cutting edge version.

[kensoh]

Rename to tagui_global.js for custom global functions instead of tagui_custom.js, to be more meaningful and representative of its purpose. Later on, can add tagui_global.csv as the global repository file.

[kensoh]

Above commit adds support for tagui_local.js for locally defined functions that are accessible to automation flows in the same folder.

Precedence is functions defined in flow script, followed by tagui_local.js (in script folder), followed by tagui_global.js (in tagui/src folder).

This feature is now usable from the cutting edge version.