Fix in exportKeypoints, exportMatches and exportTracks to handle lists.txt files with spaces.

I was trying the cvlab cars dataset [1] when I got a segfault with exportMatches.
After debugging, I found that the camera name contained spaces.

Below is an extract of my lists.txt
```
tripod_seq_02_001.jpg;376;250;301.435;NIKON CORPORATION;NIKON D70
tripod_seq_02_002.jpg;376;250;301.435;NIKON CORPORATION;NIKON D70
tripod_seq_02_003.jpg;376;250;301.435;NIKON CORPORATION;NIKON D70
tripod_seq_02_004.jpg;376;250;301.435;NIKON CORPORATION;NIKON D70
```

Thus doing 
```c++
while(in>>sValue)
```
resulted in reading 
```
tripod_seq_02_001.jpg;376;250;301.435;NIKON
CORPORATION;NIKON
D70
```

I suggest to use std::getline() to deal with this issue.

[1] http://cvlab.epfl.ch/data/pose