Fail informatively if support functions for CCA are used with CA

Several cca/rda/capscale support functions only worked with
constrained ordination, but did not check their input. This resulted
in cryptic error messages such as

Error in chol2inv(Q$qr, size = rank) :
  'size' argument must be a positive integer

Now they fail with more informative error message that tells that
the method can be used only with constrained models.
(cherry picked from commit 4d98639b1cd10a84ed41182a6e7123b84315e441)
More comprehensible error message when user asks biplots of CA

There is no biplot for CA, and its results were handled by
biplot.default that gave weird error messages. Now biplot.cca() was
added to give an informative error message. An alternative to this
would be to rename biplot.rda to biplot.cca: it already has an
error message for non-rda objects, and would only handle rda.
(cherry picked from commit 543ead1092a37e5791408bfc771d66a9f89efe28)
Fix reconstruction of response matrix in CA (no CCA) for tolerance.cca
(cherry picked from commit 0434ac4e653aeccb9b3f903a30a9fdfa55f6d7ee)