Customizable toolbar icon size

[gsomix]

Closes #513

I have introduce a lot of parameter passing to take new icon size setting into account. I'm also not sure why designer diff is so big. Auto-edits from Visual Studio 2019?

Check list:

• Add icon sizesetting into config
• Add controls to UI
• Pass the setting to theme loader, DPI scaling and UI update methods
• Add new entry to language packs
• Manually test changes

After merge:

• Create new issue about wrong tab order in setting form
• Create new issue about localization for icon size setting

[d2phap]

Thanks for very quick implementation!
There are some comments, please take a look.
I just looked at the code right now. I will pull this PR, compile, and run it tomorrow.

[fire-eggs]

The designer diff is so large because Phap works at 150% screen magnification / 144DPI. Using any other configuration causes the GUI design to become completely messed up [the designer changes all the position and sizing info].

There is some more detail in the wiki at

[gsomix]

Wow, thank you a lot! I'd finish it by myself, but have no free time till end of the week.

And thank you for the review, guys. @d2phap @fire-eggs

[d2phap]

thanks @gsomix !
I just got free time today (due to sickness 😅)