refs #9022 Proper error estimation

Evaluating problem I am having comparing two similar inelastic workspaces I've modified comparison algorithm to work with relative and absolute error. This is actually what you want comparing two workspaces and some kind of this approach was already in place for values close to 0
refs #9022 after some thinking, I've decided that standard definition

of Relerr with more careful treatment of values near 0 is preferable implementation.
refs #9022 A simple comment
Merge branch 'feature/9022_serialWorkspaceComparison' into develop