Add Unit test
WalrusFileManager: add getter for currentElem attribute (should be usefull for debug only)
WalrusFileManager: clear PHP file cache when we try to get file informations multiple time
WalrusFileManager: fix moveCurrent method path parsing and reset the current elem for emptyFolder method, fix fmFilesize method
Test: create boostrap file for PHPUnit, launch Walrus autoload and some usefull const
Test: full test for WalrusFileManager
Test bootstrap: create test directory if it doesn't exist