Feat/add kucoin spot candles feed

[tomasgaudino]

Before submitting this PR, please make sure:

• Your code builds clean without any errors or warnings
• You are using approved title ("feat/", "fix/", "docs/", "refactor/")

A description of the changes proposed in the pull request:

• Add kucoin spot candles following binance structure
• Standardize interval management (1m vs 1min vs ...)

Sadly, Kucoin hasn't developed klines with web socket yet. I'll be waiting for more updates in candles_base.py so it can handle only rest calls

Tests performed by the developer:

Tips for QA testing:

• Try using this:

# Replace in scripts/candles_example.py

eth_1m_candles = CandlesFactory.get_candle(connector="kucoin",
                                           trading_pair="ETH-USDT",
                                           interval="1m", max_records=500)
eth_1h_candles = CandlesFactory.get_candle(connector="kucoin",
                                           trading_pair="ETH-USDT",
                                           interval="1h", max_records=500)
eth_1w_candles = CandlesFactory.get_candle(connector="kucoin",
                                           trading_pair="ETH-USDT",
                                           interval="1w", max_records=50)```

[rapcmia]

Hi @tomasgaudino good day
Can you please check the failed tests below, thank you

[tomasgaudino]

Hi @rapcmia, sure!

I'll be fixing this as soon as possible :)

[rapcmia]

LGTM

• OHLC matched
• Volume and quote_asset_volume ok
• Observed some data not available yet and will be improve on future updates for the Kucoin connector

[tomasgaudino]

@rapcmia done!

[cardosofede]

LGTM!