Add posibility to run multiple JS scripts, background scripts, run script on start, task manager

[Tawank]

Proposed Changes

• Added functions to JS: runtime.toBackground(), runtime.toForeground() and runtime.isForeground() to make possible to run scripts in background or wigdets.
• Added "JS script on startup" function.
• Added task manager for JS scripts.

Types of Changes

Bugfix, New Feature

User-Facing Change

 - Added `runtime.toBackground()`, `runtime.toForeground()` and `runtime.isForeground()` to make possible to run scripts in background or wigdets.
 - Added "JS script on startup" function.
 - Added task manager for JS scripts.