Add new func syntax sugar to NFT

[tvorogme]

While contracts examples were created long time ago - there was no fancy syntax sugar like #include / #pragma version / const and some stuff was not worked as expected like elseif. Now time have come, let's see how new code style look like.

[moven0831]

Agreed. Part of compile.sh can be removed with the introducing of #include syntax

[yozarsif123]

yozarsif 123

[yozarsif123]

[Alice23caroll]

CONTRIBUTING.md

[Alice23caroll]