Get rid of ElecCore

[josephcsible]

ElecCore isn't open-source. It's visible-source, but it doesn't have a license, so it's All Rights Reserved, and @Elec332 apparently doesn't want to change this, per Elecs-Mods/ElecCore#88. We should write our own implementation of the functionality that we're using from it so we can remove it as a dependency.

[ExDomino]

Good idea, because apparently ElecCore crashs with Forestry installed together.
What fonction do you need in ElecCore? Maybe another library can provide this function.

[McJty]

What crash do you get? Eleccore and forestry are used together in many packs so I think the problem might be on your side

[Elec332]

Elecs-Mods/ElecCore#135