* Even when the tests logging handler stream is directed to `/dev/null` we still need a low logging level so that our custom logging handler, used to see if certain log messages are emitted or not, catches messages.
We defined that the amount of accepted keys should be lower than 1/4 of the system's max open file setting. Inform the user about the current situation, the logging level is "attached" to the gravity of the current status.
* `salt.modules.file.contains()`, `salt.modules.file.contains_regex()`, `salt.modules.file.contains_glob()` and `salt.utils.find` now do the searching/matching against chunks of data; using defaults, 32KB chunks of data in files; instead of searching/matching line by line.
* Based on the above changes `salt.states.file.append()`, when checking if the text to append is already present, now uses `salt.modules.file.contains_regex()` in order to match spanning multiple lines ignoring the addition/deletion of white-space or new lines, except inside commas.
* The regex used on the above item is built at runtime using `salt.utils.build_whitepace_splited_regex()`, just feed the text to it and you'll get back the proper regex to the matching/searching on, for example `salt.modules.file.contains_regex()`.
* Added tests for all this code.
This commit kind of reverts the previous "no more os.sep.join ..." commit by solving the issue which led to switching that code to `os.path.join`. Tested both on linux and windows.
