Apply inset/outset consistently in document (#775)

Different display units, or transforms on groups
no longer affect inset/outset operations.
Improvements to width calculation from Thomas Holder.

(cherry picked from commit bca6cd49, 3a9df5bc)
4 jobs for 0.92.x in 58 minutes and 51 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #487603216
inkscape:linux

00:58:51

passed #487603217
inkscape:linux-14.04

00:38:34

passed #487603219
translations

00:02:13

 
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failed continuous-integration/appveyor/branch