[max-models]

Shorter tutorial and full-example titles; the old example title moves into the description where it carried information.

• The kernels -> Kernels
• Cloud-in-cell density in 1D -> Cloud-in-cell density
• A beam's density in 2D -> Beam density in 2D
• Deposit and gather are transposes -> Adjoint deposit and gather
• An electric field from a prescribed potential -> Prescribed electric field
• Vector fields: the E x B drift -> E x B drift
• A periodic axis -> Periodic axis
• Test particles in a fixed field -> Test particles