Generic client, Browser + Node.js connections

[slvrtrn]

Summary

Further efforts after #163 (different approach).

Introduce browser connection (using native fetch) with no Node.js modules in the common interfaces. No polyfills are required. It will also be possible to write new connections on top of @clickhouse/client-common if necessary.

The client was refactored into three packages:

• @clickhouse/client-common: all possible platform-independent code, types and interfaces
• @clickhouse/client-browser: new "browser" (or non-Node.js env) connection, uses native fetch. Depends on the common package.
• @clickhouse/client: Node.js connection as it was before. Depends on the common package.

Related issues:

• Remove platform-specific dependencies #162
• Support for environments without access to http #153

Additionally, resolves #2, #17

Jest was replaced with jasmine + jasmine-expect, cause it's easier to maintain the tests that way - Karma does not like Jest very much; however, one of few downsides of that approach is that retryOnFailure does not work anymore as jasmine matchers do not throw an exception, thus in some tests I had to use janky hardcoded sleep calls.

Current browser connection limitations:

• Browser connection insert streams won't be supported atm because it does not work across all the platforms (see FF issue); arrays work fine though; select streams are also fine;
• Custom Logger currently is not implemented for the browser connection;
• Custom user-agent (with application name) is not implemented for browser connection (need to investigate what's actually possible there. Currently, I don't set it at all).

Checklist

• Unit and integration tests covering the common scenarios were added

[mshustov]

LGTM overall. What are our next steps?
There are a few follow-ups to address, at least a simple browser test for memory leaks, update docs, release beta versions, and gather feedback. Did I miss anything?

[slvrtrn]

@mshustov, I added several follow-ups to reduce the scope of this one (sorted by priority).

Before releasing the first beta (0.2.0-beta1):

• Firefox tests for browser version #179
• Release scripts for Common/Node.js/Browser packages #180
• Add browser client documentation and examples #181
• Memory leak test for browser client #182

After the first beta:

• Minified browser build #176
• Coverage for Common/Node.js/Browser packages #177

After "stable" 0.2.0:

• Don't throw in Ping command #178
• Replace Karma browser test runner #183

Please let me know if I am missing something.