Support S4 / S7(R7) documentation

[D-Se]

• Support S4 documentation shortcut
  • Find R package with documentation for S4 methods, possibly on Bioconductor
  • Design interface
  • Write tests

Progress:
The formula interface can be used to supply "2" arguments in the x argument to ?.

?combo # l = 1
?~ combo # l  = 2
?~ combo(1:10, rnorm(10)) # l = 2
? method ~ combo # l = 3

For any implementations, keep in mind that OOP system is actively being worked on, possibly deprecating S4.