added a SynologyFTP adapter
updated the tests
removed unused use statements
Moved unsupported visibility methods to a trait.
Removed unused class.
A few cs fixes
PSR-2 fixes
Cleaned up imports
Merge pull request #321 from GrahamCampbell/cs

CS Fixes
#324 fixed Adapter\Local::has return false with file_exists
Merge pull request #313 from kristianedlund/synology_ftp

added a SynologyFTP adapter
Fixed #328: SFTP and FTP setConnectionRoot is now consistent when failing.
Close ticket #322 copy and move operations in the mount manager between filesystems
Merge pull request #323 from Markcial/ticket_322

Close ticket #322
Make MountManager::copy use streams
Added @method phpdocs for default plugins
Loosened sabre/dav version restriction
Extracted plugin functionality and made the mount manager use it.
Move plugins variable to plugin trait.
Made the exception message of the NotSupportedVisibilityTrait more explicid