[dev] Splitting datatree by application

[Duck]

I started to work around the possibility of flattering DT attributes tables 
for some apps. I must say that I found great results on some preliminary 
testing. I have 1.978 DT entries mainly Agora test messages. The actual DT 
query constructed by _buildLoadQuery took 0.031s to perform. When I 
transfered the message data in a dedicated flat table it took only 0.017s! 
Nearly the half.

Duck