EntityGenerate should map column names with spaces

[programmatix]

First thank you for creating this awesome tool!

I ran mikro-orm generate-entities against my Postgres database that has columns containing spaces, and the generate entity code also has spaces that make the code non-compilable:

  @Property({ columnType: 'text', fieldName: 'Start Time', nullable: true })
  Start Time?: string;

As a quick fix replacing non-standard characters like whitespace with underscores would be great.

It would be useful in future to have options controlling column name mapping too, e.g. generating "start_time" or "startTime" instead.