support default value while import

[xuhuijun]

we are migrating data from neo4j to nebula by using csv file. There is one field which type is bool. In neo4j export csv file, the value could be true/false/empty. In such case, importing failed due to nebula reject empty value.

So we need to add default value while filed value is missing. Below is the example we want:

data.csv:
100,true,
101,,

Schema definition:
schema:
type: vertex
vertex:
tags:
- name: collection
props:
- name: used
type: bool
default: false

The second line in data will use default value false and below will load to nebula:
100(true)
101(false)

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✅ Aiee
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[yixinglu]

Thanks @xuhuijun

Could you add some test data in the examples folder to test the feature ?

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[veezhang]

@xuhuijun Thanks!I create an PR #243 to support default value, and thanks again and again.