Deprecated some functions and improved method documentation
Removed Dolibarr implementation of json_encode and json_decode, and deprecated dol_json_encode
Optimized isValidEmail function and load json.lib.php always as it contains common Dolibarr functions
Deprecated function dol_json_decode and replaced with native behaviour
Copyright
Corrected dol_microtime_float refactor
Added a test for isValidUrl function
Testing dol_json_encode is not interesting now as it uses a core function
Removed empty test
Corrected testIsValidUrl
Removed PHP 5.3 comparison in dol_nl2br function
Created test for dol_nl2br
Deprecated getStaticMember
Removed PHP 5.3 comparison in ImportCsv
Added missing return null for getStaticMember
Revert "Removed empty test"

This reverts commit cf1a2c44a359291288d7cd8f49b86ca4bb36d26a.
Restored JSON reimplementation
Revert "Testing dol_json_encode is not interesting now as it uses a core function"
Removed duplicated requires.
Json.lib.php is included with functions.lib.php
Replaced usage of dol_json_encode and dol_json_decode with json_encode and json_decode. If json module is not installed, it will refer to dol_json_encode/decode