Add section for users to ShortRef.

From conversations:

The only thing I am missing is a comprehensive reference for all labels
(eg. EP, HB, RO, MX, ...) and options (e.g. NAdapt, NTST, PtMX ...)

EP = this denotes a solution point on the boundary of the computational domain. The computation domain is defined by the maximum number of continuation steps and by any interval constraints on active continuation parameters. The initial point is always an ‘EP’ point, as is the final point.
MX = this denotes a failure of the nonlinear solver to converge and represents reaching a maximum number of iterations. The source is either a singularity, an incorrect Jacobian, or a poor initial solution guess.
HB, SN, PD, TR = these denote Hopf, saddle-node, period-doubling, and torus bifurcation points.
RO = this is only visible in the bd array and represents a regular output point, i.e., a point whose solution information is stored to disk in the data folder.

NTST, NCOL = these denote settings for the ‘coll’ toolbox that specify number of initial mesh intervals and the degree of the interpolating polynomial. Default are 10 and 4.
NAdapt = this is a setting of the ‘cont’ toolbox, i.e., the atlas algorithm, and specifies the frequency of mesh adaptation (for manifolds of dimension >=1). Default is 0.
PtMX = this is a setting of the ‘cont’ toolbox and specifies the maximum number of continuation steps (for manifolds of dimension 1, this applies in either direction of the solution manifold).

See also [#29], [#30].

Also [#27].