Repoman - ReWrite Rule and Path Normalization

[hattan]

• Repoman should have a ReWrite Rules section to allow for an explicit definition of path rewrite rules in repo.yaml instead of relying on asset rules mapping directly to source and target paths.
• Repoman path normalization should retain ./ in local relative paths. For some tooling, this is required to indicate a local path source.

[rajeshkamal5050]

@hattan I believe this is complete. Please reopen if need be.