specaccum was wrongly returning wrong weights when 'w' was not given

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/vegan/pkg/vegan@2454 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
start to make weighted specaccum a first class vegan citizen

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/vegan/pkg/vegan@2455 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
restructure nls() models i fitspecaccum

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/vegan/pkg/vegan@2458 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
fitspecaccum handles weighted models

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/vegan/pkg/vegan@2459 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
print (average) effort in weighted specaccum

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/vegan/pkg/vegan@2460 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
add basic documentation about weights in specaccum and fitspecaccum

git-svn-id: svn+ssh://svn.r-forge.r-project.org/svnroot/vegan/pkg/vegan@2461 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Merge branch 'r-forge-svn-local'