* Solves #11156

* Check file size for all file format. Disable APPEND if file is empty

* Add test for APPEND mode

- removed tr1 usage (dropped in C++17)
- moved includes of vector/map/iostream/limits into ts.hpp
- require opencv_test + anonymous namespace (added compile check)
- fixed norm() usage (must be from cvtest::norm for checks) and other conflict functions
- added missing license headers

- persistence.cpp code expects special sizeof value for passed structures
- this assumption is lead to memory corruption problems
- fixed/workarounded test to prevent memory corruption on Linux 32-bit systems

In YAML 1.0 the colon is mandatory. See http://yaml.org/spec/1.0/#id2558635.

This also allows prior releases to read YAML files created with the current version.

- one test for type_id;
- another for comments in JSON;

a JSON emitter, a parser, tests and some basic doc.

Major changes:

- modify the Base64 functions to compatible with `cvWriteRawData` and so
on.
- add a Base64 flag for FileStorage and outputs raw data in Base64
automatically.
- complete all  testing and documentation.

I could not find the cause of the error:

```
C:\builds_ocv\precommit_opencl\opencv\modules\ts\src\ts_perf.cpp(361):
error: The difference between expect_max and actual_max is
8445966.0000002384, which exceeds eps, where

expect_max evaluates to 0.9999997615814209,

actual_max evaluates to 8445967, and

eps evaluates to 1.0000000000000001e-005.

Argument "dst0" has unexpected maximal value
```

Hope this is a false alarm.

The three new functions:

```cpp
void cvStartWriteRawData_Base64(::CvFileStorage * fs, const char* name,
int len, const char* dt);
void cvWriteRawData_Base64(::CvFileStorage *
fs, const void* _data, int len);
void
cvEndWriteRawData_Base64(::CvFileStorage * fs);
```

Test is also updated. (And it's remarkable that there is a bug in
`cvWriteReadData`.)

```cpp
cvWriteMat_Base64(::cv::FileStorage & fs, ::cv::String const & name,
::cv::Mat const & mat)
```
becomes:
```cpp
CV_EXPORTS void cvWriteMat_Base64(::CvFileStorage* fs, const char* name,
const ::CvMat* mat);
CV_EXPORTS void
cvWriteMatND_Base64(::CvFileStorage* fs, const char* name, const
::CvMatND* mat);
```

Two other test are still needed.

1. Verify the Base64 data.
2. Read an old YML file for compatibility test.

1. Add Base64 support for reading and writing XML\YML file.

The two new functions for writing:

```cpp
void cvWriteRawData_Base64(cv::FileStorage & fs, const void* _data, int
len, const char* dt);
void cvWriteMat_Base64(cv::FileStorage & fs, cv::String const & name,
cv::Mat const & mat);
```

2. Change YML file header form `YAML:1.0` to `YAML 1.0`. (standard
format)

3. Add test for Base64 part.

[GSoC] FileStorage:
Add base64 support for reading and writting XML\YML file.
The two new functions:
```
void cvWriteRawData_Base64(cv::FileStorage & fs, const void* _data, int
len, const char* dt);
void cvWriteMat_Base64(cv::FileStorage & fs, cv::String const & name,
cv::Mat const & mat);
```

Conflicts:
	modules/gpu/perf/perf_imgproc.cpp

Cast a long integer to double explicitly.

Conflicts:
	modules/python/src2/cv2.cpp

Cast some matrix sizes to type int.

Change some vector mask types to unsigned.

Conflicts:
	modules/core/src/arithm.cpp