Install files used by appstream in correct package and correct path. (Closes: #981175)

Move files from /usr/share/freecad/share/* to /usr/share/* and move files from freecad-common to freecad. This should make the package more appstream compliant.

I haven't been able to test if the new package installs correctly from Gnome Software. Reading the information provided by Yvan Masson in the bug report and seeing similar software packaged, this is correct.