remove u.eig, v.eig and wa.eig items from cca.default

The cca.object was documented in vegan 1.6-10 (Sep 26, 2005), and
in that document we warn that there is "no guarantee" that these
itmems will be kept in future release. In commit bddfea39 (Mar 5, 2013)
we use harsher tone and said that the "item will be removed". However,
that harsher text has not been in any release version so that this
may be an abrupt change.
remove u.eig etc from rda
remove v.eig item from capscale result

wa.eig and u.eig already disappeared with rda changes.

The result still has CA$imaginary.u.eig (scaled scores for
imaginary axes). These are the only scores returned for
imaginary axes.
neither ade2vegancca returns u.eig, v.eig, wa.eig
man/cca.object.Rd updated to new cca object without .eig scores

There is a note about changes which here are suggested to be
effective in vegan 2.2-0.
man/cca.object tells about imaginary.u.eig scores in capscale
allow missing 'strata' in permutations

getPermuteMatrix used 'strata=NULL' to define there are no
strata. Vegan functions were adopted to this, but this broke
CRAN packages cocorresp and mpmcorrelogram. The fix was so simple
and obvious that it is almost annoying.
Do not yet warn on commsimulator deprecation

We do not yet warn on commsimulator deprecation in vegan 2.2-0
but only in the next release to give other packages time to
adapt. There were thousands of warnings in CRAN packages
bipartite and metacom.
Merge pull request #51 from jarioksa/remove-u.eig-etc

Remove u.eig etc
skeleton of NEWS about vegan 2.2-0
more NEWS picked from the ChangeLog
compile ChangeLog from git logs, long afterwards

I am not sure if we need to keep ChangeLog. This needs a bit care,
because ChangeLog is essentially linear and git is a web. However,
I collected major changes from git logs to still have a ChangeLog
of major events.
ChangeLog heading to the github time