Improved and more verbose naming convention

[ranocha]

When there are many methods, it may become complicated to distinguish them. There are some ways to approach this:

• Some methods have been used for quite some time, e.g., the IMEX methods of Ascher, Ruuth, and Spiteri. In many papers, they are called, e.g., ARS(1,1,1), ARS(2,2,2), and ARS(4,4,3). It may make sense to use this naming convention as we do (ARS111, ARS222, AS443).
• Some authors have developed multiple methods in several papers, e.g., Kennedy and Carpenter. It could also be an option to use their full names, the year of publication, and an identifier of the method, such as KennedyCarpenter2003imex3 for a third-order IMEX method from Kennedy and Carpenter (2003).
• Other libraries use somewhat more verbose names like ARKODE_ARK436L2SA_ERK_6_3_4 in SUNDIALS/ARKODE.
• OrdinaryDiffEq.jl uses abbreviations like KenCarp47.

I am not sure about the best option in the end-maybe a mix of the first and second options?