web bundle, VM2 plugin

1. VM2 dependency and implementation for executing contract in an isolated environment has been moved to a dedicated plugin, more info about how to use it in the Warp Academy.
2. A dedicated web bundle has been created in order to stop forcing the user to import a web version of the sdk (import ... from 'warp-contracts/web') when in browser. From now on, it can be imported with a regular import (import ... from 'warp-contracts'.
3. Fix for relative import in BundlerSigner class.
4. Fixes in KV API implementation.

What's Changed

• feat: move VM2 to a plugin by @asiaziola in #393
• feat: web bundle by @asiaziola in #394
• fix: Add functions to the Kv API in order to query ranges - getLessOr… by @Tadeuchi in #396

Full Changelog: 1.4.0...v1.4.1