[TypeScript] Add Object syntax overload to increment method

[lucakiebel]

The documentation for QueryBuilder#icrement says, that the method accepts columns and values either as separate arguments, or in Object syntax (the code also checks if the column is an object).

But currently this code:

knex("table")
    .where({ id: 1 })
    .increment({
      foo: 1,
      bar: 2,
    });

Throws an error:

No overload matches this call.
  Overload 1 of 2, '(columnName: string | number | symbol, amount?: number): QueryBuilder<any, number>', gave the following error.
    Argument of type '{ foo: number; bar: number; }' is not assignable to parameter of type 'string | number | symbol'.
  Overload 2 of 2, '(columnName: string, amount?: number): QueryBuilder<any, number>', gave the following error.
    Argument of type '{ foo: number; bar: number; }' is not assignable to parameter of type 'string'.

This adds an overload to the increment Method Type Definition for the case where the first argument is an Object consisting of keys from TRecord and numbers as values.

[coveralls]

Coverage: 92.392%. Remained the same when pulling 9fcfaba on lucakiebel:patch-1 into 0d27bcb on knex:master.