Replace Stack Overflow logo with material icon

[Ash]

Requested feature:

Replace Stack Overflow logo in heightmap tab material icon.

Solves the following problem:

Logo usage against Stack Overflow guidlines
"DO NOT use our logo unless you have been granted special permission by Stack Exchange Inc."

Additional information:

[dw-0]

@Ashk3000 Please point out the parts of the Stack Overflow guidlines that are violated with the use of the stack overflow (material) icon in Mainsail.

[Ash]

@Ashk3000 Please point out the parts of the Stack Overflow guidlines that are violated with the use of the stack overflow (material) icon in Mainsail.

I added the quote.

[dw-0]

@Ashk3000 Please point out the parts of the Stack Overflow guidlines that are violated with the use of the stack overflow (material) icon in Mainsail.

I added the quote.