Added Data Sources

[airon-applyinnovations]

Related to #22

Added data sources

• neon_project - fetches neon project details given project id
• neon_branches - fetches branches given project id
• neon_branch_endpoints - fetches endpoints (DB host) given project id and branch id
• neon_branch_roles - fetches available users/roles given project id and branch id
• neon_branch_role_password - fetches the password given project id, branch id and role name

I also updated acceptance test to test the new data sources and run make docu to update docs.

There are some formatting changes included in this pull request due to go fmt removing some white spaces.

[alexander-applyinnovations]

@kislerdm we are currently using this code for a production project and would appreciate if you could review, happy to incorporate any feedback