DoString binary chunks and simplifications

- Simplified DoString for strings by replacing DoString(string,string)
and DoString(string) by a single method DoString(string[,string]).
- Added DoString(byte[][,string]) to allow for usage of binary chunks.
Fix regression

Fixes regressions introduced by commit
4cfc1f2b2e8e834cfeaffcff85b0f22f2cb78f74, due to generic collection
exceptions in Metatables.checkMemberCache and Metatables.setMemberCache.
Merge pull request #17 from Mangatome/master

Regression fix + Binary chunk DoString