#334 Fix double slashes with single slashes in manifest json generation

[lprichar]

Issue

Fixes #334

Description

When converting a manifest to json the C# replaces unicode characters like ú with an ascii escape sequence that begins with \u. However the C++ json library has a bug where it double escapes \ characters so this provides a workaround the replacing \\u with \u in the C++.

Testing

The unit test Test_Unicode_CandidateNames has been adjusted to assert the correct expected values. If it passes then we're good.