Calling get_* multiple times causes dups

[boguscoder]

Parser’s getters are not guarded against multiple calls and not only repeat unnecessary parsing over and over but also populate data vectors with duplicate entries.
At least it would be nice to clean vectos before parsing
At best it may makes sense to cache results

[finixbit]

Great idea but its advisable for user calling getters to store them to prevent elf_parser.cpp from holding large parsed data within the program