Create wrapper for IDE platform icons

[rock3r]

Standalone is optional, but at least in the IDE theme we should have an easy way to address platform icons (AllIcons, StudioIcons, etc). This should be auto-generated from IDE sources.

[Walingar]

For now the way to address icons is to use Icon(key, classloader). Where the algorithm is:

1. Find class where icon placed (like AllIcons)
2. find icon there
3. copy id from there
4. Use it's class classloader

In the future IntelliJ Platform may provide just keys for Icons, so they can be used without classloader. But for now the only way is described one

[rock3r]

Is there a tracking issue for the "just provide the IDs" feature?

[Walingar]

I am not aware of such issue, it was just 1n1 discussions

[rock3r]

https://youtrack.jetbrains.com/issue/IDEA-345096/Add-way-to-obtain-icon-IDs-for-AllIcons-and-similar filed

[rock3r]

Done in #430