Do not ask to register an email address if not supported by user store

The committer/author uploader validators issued an error message upon
failed validation that suggested to the user to register a matching
email address.

Some backing user stores do not support this. In this case, this
misleading message is surpressed now.

Change-Id: I5e7f54e0a9a3586205228cde41afae2f6346a90b
Merge "Do not ask to register an email address if not supported by user store"
Add missing @Nullabe for Account in SubmoduleOp

Account can be null which was causing a 'Guice provision errors' and
preventing the Merge operation from completing. Add @Nullable for
account parameter in constructor.

Change-Id: I17103ede239190840eaffdd8aaae0bb71de3609c
Rename doc.css to doc.css.in.

As we'll need to copy it to buck-out/gen anyway, this will save some
future trouble.

Change-Id: I91cfadd15d6642a8dfaf73b6243411e9492781ca
Merge branch 'stable-2.9' into stable-2.10

* stable-2.9:
  Add missing @Nullabe for Account in SubmoduleOp
Merge branch 'stable-2.10'

* stable-2.10:
  Add missing @Nullabe for Account in SubmoduleOp
Update review command documentation for json option

Review command documentation was not accurate regarding the mutually
exclusive options in regards to json option.

Change-Id: I0ec6f1686bd7a132e8361d5837bae8e9448c41b0
Revert "Do not ask to register an email address if not supported by user store"

This reverts commit 56ba292a80694b086a6b0b5989d4609842416ea9.
Batch reindex is broken and now it requires an LDAP directory connection.

Change-Id: I944f3bcd0b20d05b82c7db4953eb3b1952da736e
Merge "Revert "Do not ask to register an email address if not supported by user store""
Merge "Update review command documentation for json option"