Update concepts.dd

The old version of isprime would return false for 2 and return true for any n with no factor less than sqrt(n).

These alterations fix that.
Make Scoped Imports appear only in D2 docs

Scoped Imports are a D2-only feature so they shouldn't appear in D1
documentation.
Merge pull request #246 from leandro-lucarella-sociomantic/scoped-imports-d1

Make Scoped Imports appear only in D2 docs
Update concepts.dd

in function isPrime: reversed the change to the condition in the loop. Changed name to isPrime in keeping with style guide.
Update concepts.dd

in isPrime: fixed braces style and corrected inequality.
Merge pull request #244 from John-Colvin/patch-1

fix the algorithm in the isprime example
Added missing dup property

For some reason dup wasn't documented for AAs.
Merge pull request #249 from John-Colvin/patch-2

Added missing dup property