API: add aliases to shorthand names e.g. `contour` for `con`

There are method names which are shorthand for words descriptive of the nature of the method, where the full word is not available as a method, for example con is the name for the contour plot method and not contour, which is not defined - likewise vect and vector. Whilst having a shorthand name is useful to save typing, it is natural to guess/try the full descriptor for a method name, therefore I think it is also important and more transparent to have the longer name available. So I suggest we have aliases to cover both the long and short versions.

Ideally the shorthand would be the alias and the longhand the canonical defined method, but since in the majority of cases (see lists below) and notably for the core user-facing plot-producing methods con, vect and traj we already have the latter, we can start by doing the opposite and in a future version perhaps switch these over - which would be transparent to the user but under-the-hood a significant code change.

So far cases I have identified where we should create an alias are, noting that due to GB/US English differences we may even want two aliases due to the use of color/colour:

• contour for con
• vector for vect
• trajectory for traj
• colourbar and colorbar for cbar
• colourscale and colourscale for cscale
• levels for levs
• gposition for gpos

and as for the converse, where there are no shorthands, perhaps:

• stip for stipple
• lp for lineplot