Textfield number input fixes.

[brachy84]

Made expression behaviour more similar to GTNHLib's parser for whole numbers, that is:

• SI prefixes for, kilo, mega, giga and terra
• b/B works for giga
• case insensitive prefixes
• % operator works.

Unfortunatly the way parsing works, we can't detect if % was actually used. Instead the maximum value is multiplied if the parsed number is a noninteger (Math.abs(value - rounded) < 0.0000001).

Additionally, I adjusted the scrolling logic to allow multiple modifiers to be active at the same time and added scroll step for ALT.

I also added a text field test to TestGuis (open with diamond).

[Miklebe]

Looked through the code, seems good. I am not the most knowledgeable guy, but so far seems like working fix and a few extra changes to add a bit more keybinds for text fields. Tested in GT5 dev env, saw no problems after changing to the new methods.