WL#5046 (PLuggable Storage Modules) - HLS updated

[Rafal Somla]

Ingo, Andreas,

I have updated HLS. You might want to check if I accurately described the 
alternatives which you suggested in your comments and if I haven't missed 
something you consider important.

Next step for this project will be to finish HLS with design for error 
reporting and string handling (Ingo already give some suggestions). Then we 
should decide which alternatives we take and then it will be show time for 
Andreas :)

Rafal