Revised xTB/Libra workflow

Major Changes

• Revised the installation instructions and CMakeLists to work with the newer version of Libint2. Added links to the installation videotutorials.
• Added the option to conduct the NBRA calculations without explicitly running many trajectories. In this case, one Hamiltonian is computed for each nuclear trajectory and re-used by many stochastic trajectories.
• Fixed the bug in the step2 of the NBRA methodology with xTB/Libra, where S AO matrices were used instead of St AO matrices.
• Fixed model Hamiltonians of Zhu in the models collection to correctly work in multi-trajectory settings
• in the QTAG: added new LHAe and BATe routines.

What's Changed

• Devel by @mdutra21 in #153
• Bug fixes + NBRA type calculations for step4 by @MohammadShakiba in #154

Full Changelog: v5.2.0...v5.2.1