Docs update concerning recent htpasswd and htdbm

additions.

Add some cross refernces between dbmmanage and htdbm.

Update man page for htdbm and htpasswd.

Add bcrypt info to misc/password_encryptions.

Backport of r1420686 from turnk.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1420732 13f79535-47bb-0310-9956-ffa450edef68