design_fieldbook: Generic fieldbook design function
In HIDAP/fbdesign: Creates a fieldbook

Generic fieldbook design function

design_fieldbook(design = "(RCBD)", trt1 = letters[1:5], trt2 = NULL,
  r = 2, k = 2, trt1_label = "trt1", trt2_label = "trt2",
  factor_name = "FACTOR", factor_lvl1 = "level1", factor_lvl2 = "level2",
  factor_lvl3 = "level3", sub_design = "crd", maxRep = 20, series = 2,
  random = TRUE, first = TRUE, cont = FALSE, zigzag = FALSE,
  variables = NULL)

`design`	a statistical design
`trt1`	vector treatment one
`trt2`	vector second treatment; a controlled factor
`r`	number of repetitions
`k`	number of blocks
`trt1_label`	string
`trt2_label`	string
`factor_name`	The name of the factor
`factor_lvl1`	The first level of the factor
`factor_lvl2`	The second level of the factor
`factor_lvl3`	The third level of the factor
`sub_design`	The sub design used by Split or Strip plot design.
`maxRep`	maximum number of repetitions
`series`	label series type
`random`	to randomize or not
`first`	to randomize or not the first repetition
`cont`	continuouse labeling
`zigzag`	order plot in serpentine
`variables`	set of variables