[dwbp] Propose to close Issue-146

  Hi all,

we had discussed a lot about the RFC terms on the BP Document.
I think we have a decision on this and we can close the ISSUE-146 [1].

A lot of inputs were given regarding this issue, and, by decision of the 
BP Editors, we agree on removing all the RFC statements and let the 
terms "should" and "must" be written as they are in plain English.

BR,
Newton

[1] 
<https://www.w3.org/2013/dwbp/track/issues/146>https://www.w3.org/2013/dwbp/track/issues/146