Import entity from CSV file

Support creating dictionary entities from imported CSV files:
- [x]  Parse first row of CSV as headers
- [x] Support large files using workers, asynchronous
- [x] Introspect column datatypes
- [x] Support for creating domains
- [x] Show example data for each attribute
- [x] Calculate max/min for numbers
- [x] Scan column data and set 'Allow Null'
