Finalize a clean documentation:
- Add features, tutorials and how-to guides in docs
- Move CLI tools from the README to a dedicated page

Clean up various parts of the code
- Rename fresh-gas to kero-prim2cons and tadia to kero-tadia
to clarify their scope
- Add c_x and h_y args to tadia_cantera to generalize hp_equil to
non-kero fuels
- Add Luche1.cti kero mechanism in INPUT for hp-equil example
- Merge example_gasout into gasout
- Rewrite gasout docstrings and clean up the code
- Create default gasout input file in INPUT
- Fix fresh_gas (now kero_prim2cons) to explicitly work with kero
only
- Recompute State energy after mass fractions are modified
- Add proper fuel name to tadia_* and yk_from_phi
- Fix tadia_cantera