Fix ethstore build

[arkpar]

Cargo 0.16.0 no longer builds ethstore binary with cargo -p ethstore.
cargo -p ethstore --bin ethstore does not work either.

[tomusdrw]

I have another fix for this, just add:

# ethstore/Cargo.toml

[lib]

[[bin]]
name = "ethstore"
path = "src/bin/main.rs"
doc = false

[arkpar]

Turns out the binary is built anyway, just to a different path. The [[bin]] section is in the toml file already.