Save adds additional quotes in 0.7.7

Use the cayley web ui to add a quad, ie

```
99 test testvalue .
```

Do a query, ie

```
g.V('99').Save("test").All()
```

Get the following result:

```
{
"result": [
{
"\\"test\\"": "value",
"id": "99"
}
]
}
```

expected:

```
{
"result": [
{
"test": "value",
"id": "99"
}
]
}
```

This was tested in 0.7.5 and does not happen.

Using windows x64 release builds.

Reproduce the example in the Cayley web UI on the Windows x64 0.7.7 release, comparing it with 0.7.5. Trace the Save("test").All() query and its JSON response; done means the result uses the key "test" rather than the escaped key "\"test\"".

Written by the indexing model from the issue text.