new fun helm-lacarte-candidate-transformer: propertize key hints with face helm-M-x-key
Merge pull request #366 from michael-heerdegen/improve-lacarte-interface

color lacarte key hints
* helm-files.el (helm-ff-auto-update-initial-value): New default value is now nil.
Bind toggle auto update to C-c <backspace> for terms users.
* helm-help.el: Document C-<backspace> usage in helm-find-files.
* helm.el (helm-match-from-candidates): Check if candidate is in hash.
* helm.el (helm-search-from-candidate-buffer): Allow using `filter-one-by-one' in candidates-in-buffer sources.
* helm-regexp.el (helm-source-buffers-list): Use now `filter-one-by-one'.
* helm.el (helm--maybe-process-filter-one-by-one-candidate): New macro.
(helm-search-from-candidate-buffer,
helm-match-from-candidates): Use it.
* helm.el (helm-match-from-candidates): No need to check cand in hash as it had been maybe modified by one-by-one filter.
* helm-regexp.el: Align let.
* helm.el (helm-output-filter--collect-candidates): Handle `filter-one-by-one', take one more arg 'source'.
* helm-grep.el (helm-do-grep-1): Use now filter-one-by-one.