Make solidity contracts available on NPM

[nugaon]

There is a project that wanted to use FDP Contracts for inclusion proofing, but there is no way to install it to a project with NPM. Currently, the @fairdatasociety/fdp-contracts NPM repository holds the code for its corresponding JS library. It could be renamed to @fairdatasoceity/fdp-contracts-js and make @fairdatasociety/fdp-contracts to include the smart contracts. After this change, dependencies of the old fdp-contract library should be updated.

[IgorShadurin]

or instead, new package could be named @fairdatasoceity/fdp-contracts-sol or @fairdatasoceity/fdp-contracts-solidity to not break projects working with old one