remove path error from 18 svg icons

There was an extra path with no line or fill colour
in these 18 icons. In some svg applications displayed
this as a square in the top righ corner of the icon.
Using return to write the logBook in UnitsCalculator
Shifting standard unit definitions
Adding Unit definition to the python modul
fixes #0001302: crash in model refine.
Merge branch 'master' of ssh://git.code.sf.net/p/free-cad/code
fixes #0001321: more visual feedback for check geometry command
+ remove .png extension in spnav dialog
+ allow to close download dialog
+ Apply Jim's fix of typos
Fix some spelling