UI Update + new functions

What's new:

• Texture generation now takes only a few milliseconds
• You will now see the complete texture at once rather than just a slice
• The amount of rows (cells) can now be changed way easier and can go up to 32
• You can set a custom resolution for your texture (max 9999 x 9999)
• You can hide the first and last cell in the texture. This prevents engines like Unity to generate weird mip maps and cause artifacts
• I've made the UI elements a bit smaller so I have more space for new settings. I know it's still ugly but it does the job

If you have more ideas for features etc. let me know!