Add quoting of paths in Paket.Restore.targets
Add quoting of paths in Paket.Restore.targets

 - Fixes failure when path contains spaces.
 - Extracted restore command to separate MSBuild variable instead of having to
   XML attribute-escape the quotes.

NatElkins/Paket,artur-s/Paket,jam40jeff/Paket,Thorium/Paket,fsprojects/Paket,thinkbeforecoding/Paket,simonhdickson/Paket,simonhdickson/Paket,vbfox/Paket,thinkbeforecoding/Paket,cloudRoutine/Paket,lexarchik/Paket,lexarchik/Paket,0x53A/Paket,isaacabraham/Paket,artur-s/Paket,lexarchik/Paket,0x53A/Paket,inosik/Paket,Stift/Paket,mrinaldi/Paket,simonhdickson/Paket,vbfox/Paket,Stift/Paket,Thorium/Paket,theimowski/Paket,snowcrazed/Paket,NatElkins/Paket,snowcrazed/Paket,baronfel/Paket,lexarchik/Paket,mrinaldi/Paket,simonhdickson/Paket,vbfox/Paket,vbfox/Paket,isaacabraham/Paket,cloudRoutine/Paket,Thorium/Paket,cloudRoutine/Paket,NatElkins/Paket,thinkbeforecoding/Paket,mrinaldi/Paket,baronfel/Paket,mrinaldi/Paket,sergey-tihon/Paket,NatElkins/Paket,isaacabraham/Paket,Thorium/Paket,0x53A/Paket,Stift/Paket,fsprojects/Paket,0x53A/Paket,Stift/Paket,sergey-tihon/Paket,cloudRoutine/Paket,snowcrazed/Paket,isaacabraham/Paket,jam40jeff/Paket,inosik/Paket,thinkbeforecoding/Paket,snowcrazed/Paket,theimowski/Paket