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ARROW-2767: [JS] Add generic to Table for column names

Adds a generic to `Table`, `StructVector,` and `Struct`, which allows a user to define their schema at compile time and get some type checking.

Includes changes from #2197

For example:
```js
import { readFileSync } from 'fs';
import { Table } from 'apache-arrow';
import { Dictionary, Float, Utf8, Int } from 'apache-arrow/type';

type Record = {
    lat: Float,
    lng: Float,
    altitude: Int,
    callsign: Dictionary<Utf8>,
}

const table = Table.from<Record>(readFileSync('./test.arrow'));

function test_number(value: number) {
    return value < 1000;
}

const row = table.get(0)!;

// error TS2345: Argument of type 'string' is not assignable to parameter of
// type 'number'.
test_number(row.callsign);
test_number(table.getColumn('callsign')!.get(0)!);

// error TS2339: Property 'foo' does not exist on type 'StructValue<Record>
// & View<any>'.
row.foo

// error TS2345: Argument of type '"foo"' is not assignable to parameter of
// type '"lat" | "lng" | "altitude" | "callsign"'.
table.getColumn('foo')

// No error
test_number(row.altitude);
test_number(table.getColumn('altitude')!.get(0)!);
```

Author: Brian Hulette <hulettbh@gmail.com>

Closes #2256 from TheNeuralBit/table-types and squashes the following commits:

67dab8ab5 <Brian Hulette> Add generic to RecordBatch.from
9fb7defc1 <Brian Hulette> Use Struct for Table accessors
e6d70131d <Brian Hulette> Remove unnecessary import/exports, thanks to TS 2.9
29c89e6bd <Brian Hulette> Add generic to DataFrame, static methods
b6fe0d418 <Brian Hulette> Add generic to Table to enable compile-time checks on column names/types