Change to allow the use of a customed linemod version

[JimmyDaSilva]

WARNING! This PR shoudn't be merged now because this would need parallel modification on ecto_linemod.

@vrabaud I found a way to use different image sizes for linemod, kinectV2 sizes for me (512x424, 960x540, 1920x1080).

We need to not use getDefaultLINEMOD because T_DEFAULTS is usually {5,8} and QHD image size for example can't be divided by 8.
https://github.com/Itseez/opencv_contrib/blob/master/modules/rgbd/src/linemod.cpp#L1825-L1840

Also like @nlyubova said the configuration file for training needs to specify the renderer window size to be the one of the kinectV2 size.

I am suggesting here that we just add new params to the config file to allow the use of a "customed linemod"

Problem was discussed on #28

Let me know what you think about this.