Refactor MooseMesh::detectPairedSidesets()
Refactor MooseMesh::detectPairedSidesets()

The old routine did not work when a "regular, orthogonal" had two
faces (e.g. -z and +z) with the same boundary id.  These boundaries
could not be set up as periodic pairs, which is OK, but they were also
preventing other periodic pairs from being detected correctly.

I think the original routine was written assuming every direction of
the mesh would have a unique id (like what you get from
MeshGeneration::build_cube()) but this restriction is not necessary,
i.e. we can still detect paired boundaries correctly on such meshes as
long as they are regular and orthogonal and the boundaries to be
periodically paired have unique ids.

Refs #7268.

bwspenc/moose,idaholab/moose,jessecarterMOOSE/moose,harterj/moose,katyhuff/moose,YaqiWang/moose,lindsayad/moose,liuwenf/moose,laagesen/moose,backmari/moose,lindsayad/moose,laagesen/moose,yipenggao/moose,idaholab/moose,YaqiWang/moose,milljm/moose,jessecarterMOOSE/moose,lindsayad/moose,harterj/moose,dschwen/moose,katyhuff/moose,liuwenf/moose,idaholab/moose,permcody/moose,Chuban/moose,andrsd/moose,yipenggao/moose,yipenggao/moose,friedmud/moose,katyhuff/moose,SudiptaBiswas/moose,joshua-cogliati-inl/moose,liuwenf/moose,dschwen/moose,backmari/moose,backmari/moose,laagesen/moose,bwspenc/moose,bwspenc/moose,katyhuff/moose,andrsd/moose,jessecarterMOOSE/moose,backmari/moose,SudiptaBiswas/moose,nuclear-wizard/moose,stimpsonsg/moose,laagesen/moose,sapitts/moose,andrsd/moose,bwspenc/moose,laagesen/moose,permcody/moose,milljm/moose,lindsayad/moose,friedmud/moose,permcody/moose,bwspenc/moose,milljm/moose,lindsayad/moose,andrsd/moose,harterj/moose,stimpsonsg/moose,joshua-cogliati-inl/moose,friedmud/moose,sapitts/moose,Chuban/moose,harterj/moose,idaholab/moose,liuwenf/moose,harterj/moose,andrsd/moose,milljm/moose,permcody/moose,dschwen/moose,idaholab/moose,Chuban/moose,joshua-cogliati-inl/moose,jessecarterMOOSE/moose,YaqiWang/moose,dschwen/moose,sapitts/moose,SudiptaBiswas/moose,stimpsonsg/moose,SudiptaBiswas/moose,milljm/moose,SudiptaBiswas/moose,nuclear-wizard/moose,sapitts/moose,friedmud/moose,liuwenf/moose,nuclear-wizard/moose,Chuban/moose,stimpsonsg/moose,sapitts/moose,dschwen/moose,liuwenf/moose,jessecarterMOOSE/moose,joshua-cogliati-inl/moose,nuclear-wizard/moose,YaqiWang/moose,yipenggao/moose