add form control. closes #532

[JanMarvin]

what does this PR provide

Initial work on form control objects (in addtion to Note the old style comments). This PR implements:

• Checkbox to create checkboxes
• Radio to create radio buttons
• Drop to create drop down menus

open TODOs not handled in this PR

As of now (MS365 Feb. 2023) there are more form control elements possible, like Button, Label, GroupBox, ScrollBar and Spinner. For the time being they are not implemented. If they are needed, PR are welcome.

Currently formCntrlDrawing() contains a lot of similar XML code segments. This surely can be cleaned up and reduced into a cleaner and smaller function. PR are welcome.

The clientData() and clientDataFC() functions should be merged into a single function. PR are welcome.

There are some more options possible when tweaking form controls (e.g. like font style and size). PR are welcome.

examples

  wb <- wb_workbook()$
    # Checkbox
    add_worksheet()$
    add_form_control(dims = "B2")$
    add_form_control(dims = "B3", text = "A text")$
    add_data(dims = "A4", x = 0, colNames = FALSE)$
    add_form_control(dims = "B4", link = "A4")$
    add_data(dims = "A5", x = TRUE, colNames = FALSE)$
    add_form_control(dims = "B5", range = "'Sheet 1'!A5", link = "B5")$
    # Radio
    add_worksheet()$
    add_form_control(dims = "B2", type = "Radio")$
    add_form_control(dims = "B3", type = "Radio", text = "A text")$
    add_data(dims = "A4", x = 0, colNames = FALSE)$
    add_form_control(dims = "B4", type = "Radio", link = "A4")$
    add_data(dims = "A5", x = 1, colNames = FALSE)$
    add_form_control(dims = "B5", type = "Radio")$
    # Drop
    add_worksheet()$
    add_form_control(dims = "B2", type = "Drop")$
    add_form_control(dims = "B3", type = "Drop", text = "A text")$
    add_data(dims = "A4", x = 0, colNames = FALSE)$
    add_form_control(dims = "B4", type = "Drop", link = "A1", range = "D4:D15")$
    add_data(dims = "A5", x = 1, colNames = FALSE)$
    add_form_control(dims = "B5", type = "Drop", link = "'Sheet 3'!D1:D26", range = "A1")$
    add_data(dims = "D1", x = letters)