Remainder of Performance considerations edit

Edited starting with "Orderer considerations" continuing through end: 
- Note in places we say collecting "enough" signatures - are there some cases where a specific signature is required in addition to number. 
- It may be useful to indicate how much better Go is than Node for performance, if they are close or not close.

Signed-off-by: Josh Horton <joshh@us.ibm.com>