Add Quick Start (full example) to keyword documentation

[bartkl]

In the keyword documentation, the keywords each have their functionality and use documented pretty thoroughly per keyword. At the top of the documentation we'd like to have a Usage or Quick Start section or something like that, which should showcase a very feature-rich, playful, varying example of all the library has to offer.

It could for example open several workbooks with or without a supplied alias, switch between them, close them, write to several sheets, read entire sheets, ranges and cells, use number formatting or not, etc. One large all-encompassing example would be perfect.

@christian-bos is there any chance of you wanting to give this a try? Or we could do it together some day. Right now I want to postpone this somehwat distant in the future, since I can't bare to look at any more documentation and I think, besides of this lack, it's pretty good as it is now.

[bartkl]

@christian-bos provided this example:

*** Settings ***
Library  ExcellentLibrary


*** Test Cases ***
Check actual sheet against base line version
    ${number of columns}  ${number of rows}  Get number of rows and columns
    Check cell values  ${number_of_columns}  ${number_of_rows}

*** Keywords ***
Get number of rows and columns
    Open workbook  file1.xlsx  alias=file1
    ${columns file1}  get column count
    ${rows_file1}  get row count
    open workbook  file2.xlsx  alias=file2
    ${columns_file2}  get column count
    ${rows_file2}  get row count
    should be equal as integers  ${columns_file1}  ${columns_file2}  Number of columns do not match
    should be equal as integers  ${rows_file1}  ${rows_file2}  Number of rows do not match
    [Return]  ${columns_file1}  ${rows_file1}

Check cell values
    [Arguments]  ${number_of_columns}  ${number_of_rows}
    :FOR  ${column_number}  IN RANGE  1  ${number_of_columns}+1
    \  Iterate per column  ${number_of_rows}  ${column_number}

Iterate per column
    [Arguments]  ${number_of_rows}  ${column_number}
    :FOR  ${row_number}  IN RANGE  1  ${number_of_rows}+1
    \  switch workbook  file1
    \  ${cell_value_sheet1}  read from cell  current_sheet  ${column_number},${row_number}
    \  switch workbook  file2
    \  ${cell_value_sheet2}  read from cell  baseline_sheet  ${column_number},${row_number}
    \  should be equal as strings  ${cell_value_sheet1}  ${cell_value_sheet2}  Values do not match (column ${column_number}, row ${row_number}) 

I would like to see some small cosmetical and neurotic changes, such as variable names with spaces instead of underscores and replacing Check with Get and changing Iterate to something more conceptual.

Other than that this example seems fine.