R: new API to create graphs, #730

R: fix doc typo

R make: Constructor sketch,to be updated

R: make: implement make_ & co

Looks very good, actually. Now some tests, and the rest.

R make: simple tests, bugfix when no paraters

R: renaming some constructors, preparing for make

R make: fix deprecation typos from renaming

R make: add many more deterministic constructors

Probably most.

R make: add more functions, formula -> literal
Merge pull request #733 from igraph/r-make

R: new API for creating graphs, #730