revert changes to fbbc76f2 because master is very unstable right now

files_encryption app is now enabled in enable_all.php

disabled encryption file proxy in test/lib/cache/file.php

instanceid is generated by uniqid() and then used as the
session_name. Because session_name requires at least one letter
and uniqid() does not guarantee to provide that, in the case that
uniqid() generates a string of only digits, the user will be stuck
in an infinite login loop because every request will generate a
new PHP session.

Move testcase for getDefaultEmailAddress with mail_domain set in config.php to own test function.

see #2499

fixing copy operation on mapper

adding a new test class for mapped local using a dot in the datadir - reflects the issue described in #1659

initial version of a local storage implementation which will use unique slugified filename on the local filesystem.
This implementation will only be enabled on windows based system to solve the issues around UTF-8 file names with php on windows.