More detailed error messages when using fr-config-push

[jonathanhuynh70]

I think the current error messages could include the problematic file in their error message as well
For example:

fr-config-push themes
Updating themes
Unexpected non-whitespace character after JSON at position 4458 (line 150 column 2)

[christian-brindley]

In general, exceptions are unhandled, forcing the tool to terminate on error. In the case of loading JSON, we could provide a more helpful message like

Error loading JSON from file openam-brindley-config/realms/alpha/themes/Blank/Blank.json: Unexpected non-whitespace character after JSON at position 7073 (line 264 column 2)

This requires a wrapper function for all occasions where we load JSON from a file - e.g.

function loadJsonFromFile(path) {
  try {
    return JSON.parse(fs.readFileSync(path));
  } catch (e) {
    console.log(`Error loading JSON from file ${path}: ${e.message}`);
    process.exit(1);
  }
}
...
        const theme = loadJsonFromFile(
          path.join(themePath, `${themename}.json`),
        );