Fix reading of 1904 dates option

Whether the spreadsheet is using 1904 dates or not is controlled by a XML property. Its value can be the string "false" that is not mapped to the boolean "false" but to the boolean "true"... Therefore Spout was previously using the wrong date system when this property was set.

Merge branch 'master' into develop_3.0

Change Worksheet function visibility from private to protected in ord…

…er to class extending. We have created small package on top of the Spout for support cell number format and per cell styles.

Prevent error when close() called while writer already closed (box#402)

Fix crash when using associative array with empty row (box#354)

Move ReaderCommonOptions class to Common folder (box#343)

Apply custom style to empty cells if needed (box#307)

Fixes box#295

If a row should be written with a custom style, the handling of empty cells should change.
Instead of being skipped entirely, empty cells will be applied the custom style, if this style has custom background color or borders.
If not, then the cell definition can still be skipped.

Shared strings table without uniqueCount and count should work (box#269)

Use file based strategy in this case

Merge pull request box#199 from box/check_valid_resource_on_close

Check file handle is valid before manipulating it

Merge pull request box#187 from skeleton/issue-183

Fix line breaks on CSV reader