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.
7b1f7c8d8e