Word weights not normalized when generating BowVectors

[clementjambon]

I've noticed that the weights of the words in the fbow map are computed without any form of normalization.

fbow/src/fbow.h

Line 434 in e148dbc

r1[bn_info->getId()]+=bn_info->weight;

What's more, it appears that the vocabulary itself is not normalized.

This is quite inconsistent, especially regarding DBoW2 implementation where every bag of words is normalized upon its generation: https://github.com/dorian3d/DBoW2/blob/3924753db6145f12618e7de09b7e6b258db93c6e/include/DBoW2/TemplatedVocabulary.h#L1191

It it thus not suprising to see that loop closure and relocalization do not seem to work properly in frameworks like openvslam as highlighted by several issues including the following: #31 (comment)