Remove calculated properties to make recalculate formulas in some spreadsheet applications, such as Kingsoft WPS

Exported function to convert excel date to time

Signed-off-by: NVaibhav Nayak <vaibhav.nayak@gmail.com>

Reduce redundant memory copy in getRowHeight

AddPivotTable API changed: new structure PivotTableField to hold pivot table fields for better scalability

- typo fixed and update do.dev badge in the README.

Resolve #580, revert commit https://github.com/360EntSecGroup-Skylar/excelize/commit/5ca7231ed408ac264f509ff52b5d28ff4fbda757

SetColVisible() can parse a column range + typos.

* Support all datatypes for StreamWriter

* Support setting styles with StreamWriter

**NOTE:** This is a breaking change. Values are now explicitly
passed as a []interface{} for simplicity. We also let styles to be
set at the same time.

* Create function to write stream into a table

* Write rows directly to buffer

Avoiding the xml.Encoder makes the streamer faster and use less
memory.

Using the included benchmark, the results went from:

> BenchmarkStreamWriter-4   514  2576155 ns/op  454918 B/op  6592 allocs/op

down to:

> BenchmarkStreamWriter-4  1614   777480 ns/op  147608 B/op  5570 allocs/op

* Use AddTable instead of SetTable

This requires reading the cells after they have been written,
which requires additional structure for the temp file.

As a bonus, we now efficiently allocate only one buffer when
reading the file back into memory, using the same approach
as ioutil.ReadFile.

* Use an exported Cell type to handle inline styles for StreamWriter

# Conflicts:
#	rows.go
#	sheet.go

* Fixed issue #539 Fixed error opening excel file created in encoding different from UTF-8, added logging of possible errors when decoding XML if the function does not provide exit with an error

* Added test for CharsetReader

* Fixed #discussion_r359397878

Discussion: https://github.com/360EntSecGroup-Skylar/excelize/pull/540#discussion_r359397878

* Fixed go fmt

* go mod tidy and removed unused imports

* The code has been refactored

Fix #533, add support overlapped mergecells