Ensure the list of ids is unique in BoundaryInfo::add_{side,node}().
Ensure the list of ids is unique in BoundaryInfo::add_{side,node}().

Use std::make_pair instead of temporary variables in a few instances.

Refs #706.

BalticPinguin/libmesh,aeslaughter/libmesh,svallaghe/libmesh,dmcdougall/libmesh,giorgiobornia/libmesh,libMesh/libmesh,balborian/libmesh,hrittich/libmesh,giorgiobornia/libmesh,friedmud/libmesh,dschwen/libmesh,aeslaughter/libmesh,aeslaughter/libmesh,coreymbryant/libmesh,dmcdougall/libmesh,giorgiobornia/libmesh,coreymbryant/libmesh,libMesh/libmesh,jwpeterson/libmesh,dschwen/libmesh,capitalaslash/libmesh,benkirk/libmesh,aeslaughter/libmesh,dmcdougall/libmesh,giorgiobornia/libmesh,90jrong/libmesh,balborian/libmesh,dmcdougall/libmesh,jwpeterson/libmesh,giorgiobornia/libmesh,capitalaslash/libmesh,aeslaughter/libmesh,jwpeterson/libmesh,vikramvgarg/libmesh,friedmud/libmesh,libMesh/libmesh,90jrong/libmesh,benkirk/libmesh,dknez/libmesh,vikramvgarg/libmesh,giorgiobornia/libmesh,hrittich/libmesh,libMesh/libmesh,benkirk/libmesh,pbauman/libmesh,dschwen/libmesh,capitalaslash/libmesh,90jrong/libmesh,friedmud/libmesh,dknez/libmesh,roystgnr/libmesh,BalticPinguin/libmesh,balborian/libmesh,jwpeterson/libmesh,dschwen/libmesh,vikramvgarg/libmesh,vikramvgarg/libmesh,pbauman/libmesh,benkirk/libmesh,capitalaslash/libmesh,dknez/libmesh,benkirk/libmesh,svallaghe/libmesh,pbauman/libmesh,90jrong/libmesh,svallaghe/libmesh,vikramvgarg/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,dmcdougall/libmesh,capitalaslash/libmesh,coreymbryant/libmesh,balborian/libmesh,coreymbryant/libmesh,BalticPinguin/libmesh,BalticPinguin/libmesh,giorgiobornia/libmesh,jwpeterson/libmesh,dschwen/libmesh,friedmud/libmesh,dknez/libmesh,BalticPinguin/libmesh,pbauman/libmesh,balborian/libmesh,libMesh/libmesh,roystgnr/libmesh,hrittich/libmesh,benkirk/libmesh,90jrong/libmesh,benkirk/libmesh,hrittich/libmesh,pbauman/libmesh,roystgnr/libmesh,hrittich/libmesh,balborian/libmesh,90jrong/libmesh,svallaghe/libmesh,dknez/libmesh,balborian/libmesh,svallaghe/libmesh,90jrong/libmesh,coreymbryant/libmesh,hrittich/libmesh,benkirk/libmesh,capitalaslash/libmesh,friedmud/libmesh,jwpeterson/libmesh,hrittich/libmesh,dschwen/libmesh,friedmud/libmesh,vikramvgarg/libmesh,vikramvgarg/libmesh,vikramvgarg/libmesh,90jrong/libmesh,libMesh/libmesh,pbauman/libmesh,90jrong/libmesh,hrittich/libmesh,dschwen/libmesh,svallaghe/libmesh,coreymbryant/libmesh,jwpeterson/libmesh,hrittich/libmesh,svallaghe/libmesh,dmcdougall/libmesh,aeslaughter/libmesh,BalticPinguin/libmesh,dknez/libmesh,giorgiobornia/libmesh,giorgiobornia/libmesh,dknez/libmesh,balborian/libmesh,balborian/libmesh,jwpeterson/libmesh,capitalaslash/libmesh,benkirk/libmesh,dknez/libmesh,svallaghe/libmesh,aeslaughter/libmesh,friedmud/libmesh,coreymbryant/libmesh,pbauman/libmesh,roystgnr/libmesh,svallaghe/libmesh,pbauman/libmesh,libMesh/libmesh,roystgnr/libmesh,aeslaughter/libmesh,capitalaslash/libmesh,vikramvgarg/libmesh,dmcdougall/libmesh,aeslaughter/libmesh,coreymbryant/libmesh,pbauman/libmesh,roystgnr/libmesh,dschwen/libmesh,friedmud/libmesh,balborian/libmesh,libMesh/libmesh,dmcdougall/libmesh,BalticPinguin/libmesh,roystgnr/libmesh,friedmud/libmesh