Allow installing package from git

[vsbogd]

This is to allow referring from dependent projects (such as snet-cli or snet-daemon) to latest github version without publishing it to the npm package registry.

To do so npm install hook is added which runs npm run package-npm command. .npmrc file is used to distinguish local npm install and one running from dependent project. When package is installed as dependency this file is not downloaded because it is not listed in files section of the package.json. Thus package-npm.js which runs from dependent project installs abi to package root directory and when package-npm.js is started from cloned platform-contracts repository it copies files to build/npm-module.

[astroseger]

I think that putting ABI files to github was an error at the first place. If we will update them at each commit then size of the repo will grow without a limit. It is not a right way of using git. So I would propose to remove build/contracts/*.ABI at all. @tiero and @vforvalerio87, I know that it was some reason to put ABI at github, but there is, certainly, should be an other way to solve these problems, without misusing git.
So, in light of above, I don't like this solution because it require putting ABI at github. I think that, for now, the way with separate "dev" installation script, which takes platform-contract ABI from already installed contracts would be better (see scripts/install_dev.py in snet-cli).

But:

1. In the future, @ksridharbabuus will probably change installation procedure in any way.
2. We don't have much time now.

So if you already have an installation procedure for daemon which use this solution, then I propose:

1. merge this pull requiest (but please update ABI first, I'm going to merge pull request Switch expiration to blocknumber in MultiPartyEscrow #50 now)
2. Create an issue about removing ABI from github, and update installation process for the whole project

[vsbogd]

Then I would propose compiling contracts after installing npm package as dependency. It will not require adding compiled contracts into repository.

Separate dev script is not unified with npm which is used to install dependencies at the moment. It additionally requires changes in .circleci configuration, additional manual instructions (how to build with and without dev dependency). And these things should be done in each repo which uses platform-contracts.

This change instead requires only pointing on new dependency in npm configuration:

$ git diff resources/blockchain/package.json
diff --git a/resources/blockchain/package.json b/resources/blockchain/package.json
index 6c21d60..5bc7c4b 100644
--- a/resources/blockchain/package.json
+++ b/resources/blockchain/package.json
@@ -3,7 +3,7 @@
     "bip39": "2.5.0",
     "fs-extra": "5.0.0",
     "ganache-cli": "6.1.6",
-    "singularitynet-platform-contracts": "0.2.1",
+    "singularitynet-platform-contracts": "github://singnet/platform-contracts#af9a198a4fd519f45944ace3f636931fbdfa5dec",
     "singularitynet-token-contracts": "2.0.0",
     "truffle": "4.1.13",
     "truffle-contract": "3.0.6",

[vsbogd]

As @astroseger proposed, I am merging it for now, and opening issue to discuss and find a better solution #53