[General] Up compat

[ocots]

• CTModels 0.6
• CTDirect 0.15

[ocots]

@PierreMartinon

•  Update the page: https://control-toolbox.org/OptimalControl.jl/dev/manual-solve.html. New modeller, etc.
• Update the exported functions:

OptimalControl.jl/src/OptimalControl.jl

Lines 133 to 136 in e583d34

	# CTDirect
	import CTDirect: CTDirect, direct_transcription, set_initial_guess, build_OCP_solution
	export direct_transcription, set_initial_guess, build_OCP_solution