* 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

Reduce allocations when writing

Fix #494

If a row is full, don't bother allocating a new one, just return it.

Use the last populated row as a hint for the size of new rows.

Simplify checkSheet to remove row map

* Added accessors for Getting/Setting Page Margins

* Added test cases

solve ending space missing

Add missing ShowZeros SheetViewOption implementation

* 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.