[dist] README.SETUP: memcached is mandatory now

memcached is not optional anymore it is mandatory for the webUI to work.
[api][backend] log buildhistory of patchinfos and check last version got build before release

fixes bnc#879793
[dist] update gem versions
[backend] Optimize sourcedeletion function

Optimization done in runtime at revfile rewrite process and do
not fail if a project was deleted during (long) run
[backend] fix typo in update_dst_full refresh operation
[api] cleanup channel recreation code a bit
[backend] do not put imported binaries into patchinfos
[backend] be more careful with channels and patchinfos, they must not get put into useforbuild

Fixes the event_useforbuild handling as side effect...
[backend] fix nouseforbuild marker regeneragtion
[api] store channel set in package object
[dist] Update README for latest release

+ Clean up a couple of typos and trailing spaces.
[webui] Improvements in comment display

 * @user in the body is now a link
 * Use user_with_realname_and_icon to display the author
 * Mails are sent with multipart in plain text and html
 * Layout for the html version of the mails
[webui] update to codemirror 4.2
[backend] another .nouseforbuild check for completeness
[dist] do not fail on SLES 11 SP3, disabled mysql timeout during tests
[backend] transport link chain in remote_getrev if the expansion failed

Should help with stuck 'service in progress' errors.
[api] Fix ldap incorrect use of 'login' variable
[api] Fix 'user_ldap_strategy.rb' unable to call 'logger.debug' method

make direct call to Rails.logger.debug instead of logger.debug
[dist] Allow overriding initrd without overriding kernel
[webui] Visual improvement to the monitoring page