* Add benchmark for adding images to sheet

This should help track performance regressions in future changes.

* Only transform sheet name if necessary

This allows the user to set a floating point value into a
cell with a specific number of places after the decimal.

Closes #357

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

update go test and function docs

* update README and functions docs

* update README and functions docs

* 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

fix: datavalidation list error, formula > 255 issue #339

The function SetPageLayout support set paper size

Resolve #333 New feature: File.DuplicateRowTo() duplicate row to a specified row position

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.

Do not create a blank fill if no fill is specified in the style format

Resolve #318, add new functions `SetPageLayout` and `GetPageLayout`

* #195: proposed resolution to the issue

* Make GetRows return value avoid empty cell

* Update test file to fix broken testing.

Add license scan report and status

Signed-off-by: Nfossabot <badges@fossa.io>

Tests refactoring

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