Support naming rings and ideals on creation

[coneill-math]

> R <- ring("a", "b", "c", name = "R")
> m2_parse("R")
M2 Symbol: R

[coneill-math]

Some other functions may be missing this parameter as well.

[dkahle]

Actually, isn't this right? By itself, "R" is simply a symbol. For m2_parse() to parse it into the full ring, it'd need to get the output of toExternalString on R.

[coneill-math]

The idea is to use the specified name in place of the m2rint00000001. I believe matrix() uses this parameter currently, though perhaps I am mistaken.