small improvement to vigra.__doc__ (sub-module overview and fall-back doc URL)
small improvement to vigra.__doc__ (sub-module overview and fall-back doc URL)

capturePointer/vigra,capturePointer/vigra,cbecker/vigra,dagophil/vigra,cha007/vigra,funkey/vigra,xiwei-zhang/vigra,mmuellner/vigra,martinsch/vigra,psteinb/vigra,dagophil/vigra,cha007/vigra,psteinb/vigra,martinsch/vigra,hmeine/vigra,kod3r/vigra,psteinb/vigra,kod3r/vigra,dstoe/vigra,xiwei-zhang/vigra,cha007/vigra,cbecker/vigra,kod3r/vigra,xiwei-zhang/vigra,dagophil/vigra,psteinb/vigra,psteinb/vigra,xiwei-zhang/vigra,mmuellner/vigra,dstoe/vigra,ThomasWalter/vigra,capturePointer/vigra,stuarteberg/vigra,hmeine/vigra,capturePointer/vigra,hmeine/vigra,ThomasWalter/vigra,cbecker/vigra,dagophil/vigra,ThomasWalter/vigra,DaveRichmond-/vigra,cha007/vigra,dagophil/vigra,mmuellner/vigra,DaveRichmond-/vigra,kod3r/vigra,funkey/vigra,stuarteberg/vigra,stuarteberg/vigra,DaveRichmond-/vigra,cbecker/vigra,stuarteberg/vigra,cha007/vigra,timoMa/vigra,DaveRichmond-/vigra,dstoe/vigra,kod3r/vigra,DaveRichmond-/vigra,martinsch/vigra,martinsch/vigra,timoMa/vigra,capturePointer/vigra,mmuellner/vigra,ThomasWalter/vigra,funkey/vigra,stuarteberg/vigra,ThomasWalter/vigra,ThomasWalter/vigra,martinsch/vigra,capturePointer/vigra,timoMa/vigra,kod3r/vigra,timoMa/vigra,stuarteberg/vigra,dstoe/vigra,dstoe/vigra,hmeine/vigra,hmeine/vigra,mmuellner/vigra,ThomasWalter/vigra,psteinb/vigra,martinsch/vigra,cha007/vigra,funkey/vigra,DaveRichmond-/vigra,dstoe/vigra,xiwei-zhang/vigra,mmuellner/vigra,psteinb/vigra,dstoe/vigra,mmuellner/vigra,timoMa/vigra,stuarteberg/vigra,hmeine/vigra,funkey/vigra,capturePointer/vigra,dagophil/vigra,hmeine/vigra,kod3r/vigra,timoMa/vigra,cbecker/vigra,xiwei-zhang/vigra,dagophil/vigra,timoMa/vigra,cbecker/vigra,funkey/vigra,xiwei-zhang/vigra,DaveRichmond-/vigra,funkey/vigra,cha007/vigra