Only export Projection instance

[fredj]

This is breaking change, to be discussed.

old:

import code, {proj} from '@geoblocks/proj/src/EPSG_2056.js';

const the_projection = proj;
const name = code;

new:

import proj from '@geoblocks/proj/src/EPSG_2056.js';

const the_projection = proj;
const name = proj.getCode();