Revert "Upgrade to SpongeAPI 1.1-SNAPSHOT and use their Maven repository"

This reverts commit 91042860ed64a18435f4b5d35abc334f087e638a.

Revert "Add note about gradlew on windows"

This reverts commit 21611543ebbf55c858ec12acc75403bf6801fba1.

Revert "Update README to remove initializing submodule"

This reverts commit 975c27d8253e732c02bb65310a0fd3852f650632.

Revert "Delete old SpongeAPI submodule"

This reverts commit a93e50d9eac7ad932c24902fb839543c9affa80b.
Update to SpongePowered/SpongeAPI@7657f82e159e043c27166ee765d17f52c5e9924f