Improve efficiency of exp3 and exp6 operations

[core] Efficient implementation of exp6

This new expression comes from the fact that [w]x*[w]x = w*w.T -
\|x\|^2. For more information see "Differential of the Exponential Map":
http://ethaneade.org/exp_diff.pdf

Change differentiate into difference

Differentiate was not the right term as it is devoded to differential calculus.
This is related to #432.

Remove warnings in unit tests

Change naming of LieGroupTpl and LieGroupOberationBase

It follows #432 suggestions

Update API of Python bindings

[CI][Gitlab] Use a dedicated target for generating doc and coverage

Remove lab directory

Fix bug in Python interpreter

Remove now useless dependency to HPP-MODEL_URDF and METAPOD

METAPOD is now outdated.
Installing it on recent platforms is now tedious.
The results was only compared for Symmetric3 class.

As HPP relies on Pinocchio since 2 years, it seems natural to remove the dependency.
Check and benchmark are no more meaningfull.

Add version utils to check the current version of Pinocchio

This feature mimics the Eigen checking of version