don't specify path to 3rdparty directory when registering Pimple autoloader

The core 3rdparty directory is in the include_path from lib/base.php anyway, so this is unnecessary, and causes problems for downstream distributors who unbundle Pimple.
Merge pull request #6598 from lolozere/master

Add support mimetype
Merge pull request #6601 from AdamWill/pimple-include

don't specify path to 3rdparty directory when registering Pimple autoloader
[tx-robot] updated from transifex
Return SPACE_UNKNOWN if disk_free_space is disabled when getting the free space on a local storage
Merge pull request #6513 from owncloud/user-no-change-displayname

Re-add the config options to remove the ability for users to change their displayname
Make OC_Avatar unit tests independent of currently loggedin user
Fix APCIterator syntax in \OC\Memcache\APCU::clear

see http://www.php.net/manual/en/apciterator.construct.php
Merge pull request #6609 from owncloud/avatar-test-user

Make OC_Avatar unit tests independent of currently loggedin user
Merge pull request #6605 from owncloud/free_space_disabled

Return SPACE_UNKNOWN if disk_free_space is disabled
Merge pull request #6610 from owncloud/apcu-clear

Fix APCIterator syntax in \OC\Memcache\APCu::clear
[tx-robot] updated from transifex
Merge branch 'master' into fix-5388-master
Fix PostgreSQL port configuration on install
[tx-robot] updated from transifex
Merge pull request #6580 from monreal/master

Silence output of 'which' command used in smbclient detection
Add tabs to conformance with owncloud code standards
Merge pull request #6031 from s0taka/master

No decimal points for Kilobyte and Byte #5371.
require composer's autoload.php if present
reference 3rdparty branch with SabreDAV 1.7.9 installed using composer