Create relative directory (__dirname) and filename (__filename) path utlis

[u-ways]

We noticed that Deno does not have __filename and __dirname (different than Deno.cwd) node equivalents.
This is cause of Deno's awesome import API allowing more URL flexibility.

Therefore this userstory is for creating a path utlis for a consistent way to reference file paths.

Acceptance:

• Use the import API.
• Create a function to get the relative (to file) working directory path.
• Create a function to get the relative filename path.

[u-ways]

Implementation: See commits referenced above.

Changes:

• Add path_utils.ts to get relative filename and directory path using import.meta.
• Add denon test script that runs backend acceptance tests.
• Append Deno's *_test.ts convention to test files. (See Deno's issue #20 for more information)