Enable flatbuffer to initialize Parser from bfbs (#4283) (#5077)

* Enable flatbuffer to initialize Parser from bfbs (#4283)

Now its possible to generate json data from bfbs data type and flatbuffers data
and visa versa.

* add deserialize functionality in parser from bfbs
* add small usage sample

* Fix build break

* Merge branch 'pr/1' into fix-issue4283

* Fix buildbreak

* Build monster_test.bfbs with --bfbs-builtins

Attribute flexbuffer has be included in bfbs. Only with this attribute test
will run. By initialization a parser by a bfbs the attribute has to be known
for this filed. monsterdata_test.golden has a flexbuffer field so parse would
fail.

* Fix generate_code.sh

* Revert automatic indent changes by IDE

* Auto detect size prefixed binary schema files

* Use identifier (bfbs) to detect schema files

include/flatbuffers/flatc.h

@@ -80,6 +80,9 @@ class FlatCompiler {
                  const std::string &contents,
                  std::vector<const char *> &include_directories) const;
 
+  void LoadBinarySchema(Parser &parser, const std::string &filename,
+                        const std::string &contents);
+
   void Warn(const std::string &warn, bool show_exe_name = true) const;
 
   void Error(const std::string &err, bool usage = true,