Auxiliary classes StdObjMgt_ReadData::Object and StdObjMgt_WriteData::Object are renamed to "ObjectSentry" (to better reflect their nature); constructor is made explicit to ensure that such objects are always created intentionally.
These objects are instantiated explicitly in the body of relevant functions, instead of implicit creation as temporary objects when function requires such object as argument.
Variable used to get char from stream is nullified in several places in FSD_File and other classes, to avoid possible usage of uninitialized memory in case if stream is bad.
1. Bug fix in reading old persistent data using FSD_File storage driver
2. Persistence compatible with legacy format was restored for shapes
a. Implemented a storage read / write wrapper for legacy persistence
b. Added DRAW commands to read / write files in legacy format
c. Added test cases for reading / writing operations with checking number of sub-shapes and physical properties
d. Updated related sections of the development guide
