* Allow access to more formula attributes in SetCellFormula

Make SetCellFormula variadic to not break API.
The new arguments are option arguments in which the type of
the formula and the ref attribute may be set.
These need to be set for an array formula to work.

* Add TestWriteArrayFormula to test optional parameters of SetCellFormula

TestWriteArrayFormula writes a document to the test directory that
contains array formulas that are used to calculate standard deviations.
The file also contains values calculated by the Go testcase, so the
results can be verified. It should be tested, if the array formula
works (i.e. shows a number, not an error) and that the values calculated
by the formula and those calculated by Go are the same.

The inline string struct is actually the same
as the shared strings struct, reuse it.

Note that Go version 1.10 is required.

Fixes #462

Instead of re-encoding the full sheet to change the namespaces
in the encoded bytes, read the sheet again and do the byte
replacements there.

In this case, file access ends up being more performant than
marshaling the sheet back to XML.

In the SharedStrings test, ensure the strings are actually read.

Fix #439

- Testing case for set and get doc properties
- Update charts struct XML tags

typo fixed

add error return value

exported functions:

GetMergeCells
ProtectSheet
UnprotectSheet
UpdateLinkedValue
GetMergeCells
SetSheetVisible

inner functions:

workSheetReader
copySheet

Exported functions:

SetCellStyle
InsertCol
RemoveCol
RemoveRow
InsertRow
DuplicateRow
DuplicateRowTo
SetRowHeight
GetRowHeight
GetCellValue
GetCellFormula
GetCellHyperLink
SetCellHyperLink
SetCellInt
SetCellBool
SetCellFloat
SetCellStr
SetCellDefault
GetCellStyle
SetCellValue
MergeCell
SetSheetRow
SetRowVisible
GetRowVisible
SetRowOutlineLevel
GetRowOutlineLevel
GetRows
Columns
SearchSheet
AddTable
GetPicture
AutoFilter
GetColVisible
SetColVisible
GetColOutlineLevel
SetColOutlineLevel
SetColWidth
GetColWidth

inner functions:

adjustHelper
adjustMergeCells
adjustAutoFilter
prepareCell
setDefaultTimeStyle
timeToExcelTime
addDrawingChart
addDrawingVML
addDrawingPicture
getTotalRowsCols
checkRow
addDrawingShape
addTable

typo fixed and go test updated

* Huge refactorig for consistent col/row numbering

Started from simply changing ToALphaString()/TitleToNumber() logic and related fixes.
But have to go deeper, do fixes, after do related fixes and again and again.

Major improvements:

1. Tests made stronger again (But still be weak).
2. "Empty" returns for incorrect input replaces with panic.
3. Check for correct col/row/cell naming & addressing by default.
4. Removed huge amount of duplicated code.
5. Removed ToALphaString(), TitleToNumber() and it helpers functions at all,
and replaced with SplitCellName(), JoinCellName(), ColumnNameToNumber(), ColumnNumberToName(), CellNameToCoordinates(), CoordinatesToCellName().
6. Minor fixes for internal variable naming for code readability (ex. col, row for input params, colIdx, rowIdx for slice indexes etc).

* Formatting fixes

* Implement consistent row addressing by Excel row number starting with 1

1. Added second versions for all row manipulation methods with zero-based row addressing.
2. Fixed methods documentation to explicitly describe which row addressing used in method.
3. Added WARNING to README.md.
4. Cosmetic change: All row test moved to file `rows_test.go`.

* TravisCI: go1.12 added to tests matrix

* BACKWARD INCOMPARTIBLE: Use only Excel numbering logic from 1 row

* README updated

* TestTitleToNumber: more test cases

* TitleToNumber: drop use of math.Pow()

Compute using pure integers

* TitleToNumber: simplify

Remove unecessary casts to int

DuplicateRowTo() is similar to DuplicateRow() but copies specified row not just after specified source row
but to any other specified position below or above source row.

Also I made minor modifications of tests: using filepath.Join() instead of direct unix-way paths strings
to avoid possible tests fails on other OS.

Primary motivation: Avoid statefull tests with not ignorable git file tree changes.
Multiple tests reads and overwrites signle file for won needs.
Multiple tests reads and overwrites file under version control.

Secondary motivation: Minimal tests logic aligment, separate error expectation
and not error expectation tests. Introduce sub-test over test data sets and so far.

This commit is not ideal but necessary (IMHO)

* go mod tidy applied

* File.DuplicateRow() method added