Fix a case when extension less file is importing other less files

I wanted to split less file my extension is using into more files, but loading failed when using valid import directives. Through debugging, I found out that some properties of file info were not filled as it should.

These are the values for file `brackets.less`:
```
currentDirectory: "file:///D:/Program%20Files/Brackets/dev/src/styles/"
entryPath: 	      "file:///D:/Program%20Files/Brackets/dev/src/styles/"
filename: 	      "file:///D:/Program%20Files/Brackets/dev/src/styles/brackets.less"
relativeUrls:     undefined
rootFilename: 	  "file:///D:/Program%20Files/Brackets/dev/src/styles/brackets.less"
rootpath:         "file:///D:/Program%20Files/Brackets/dev/src/styles/"
```

And these are the original values calculated for `brackets-git.less`:
```
currentDirectory: ""
entryPath:        ""
filename:         "brackets-git.less"
relativeUrls:     undefined
rootFilename:     "brackets-git.less"
rootpath:         "file:///C:/Users/Zaggi/AppData/Roaming/Brackets/extensions/user/zaggino.brackets-git/less/"
```

The fix makes fileInfo look the same way as in the `brackets.less` case and all references are loaded correctly.