Shaarli API first step

[ArthurHoaro]

Related to #609:

• Add the API settings in Shaarli administration and install forms (enabled/secret).
• API implementation structure, with unit tests.
• Implement 1 service for now: /info.
• Plug the API to be able to reach it.

You can test it with any REST client with:

• http://instance/api/v1/info behind an Apache server.
• http://instance/?do=api&version=1&test=fee&q=/info2 otherwise.
• A valid JWT token in a header call jwt.

You can use this script to get a valid token easily (they're valid during 9 minutes):

<?php

function generateJwtToken($secret)
    {
        $header = base64_encode('{
            "typ": "JWT",
            "alg": "HS512"
        }');
        $payload = base64_encode('{
            "iat": '. time() .'
        }');
        $signature = hash_hmac('sha512', $header .'.'. $payload , $secret);
        return $header .'.'. $payload .'.'. $signature;
    }

echo generateJwtToken('jaimeLePate');

You can add this in you config file to get more info about the errors:

"dev": { "debug": true }

EDIT: @nodiscc regarding shaarli/api-documentation#1

cloc application/api
       4 text files.
       4 unique files.                              
       0 files ignored.

github.com/AlDanial/cloc v 1.70  T=0.01 s (308.8 files/s, 49942.3 lines/s)
-------------------------------------------------------------------------------
Language                     files          blank        comment           code
-------------------------------------------------------------------------------
PHP                              4             59            274            314
-------------------------------------------------------------------------------
SUM:                             4             59            274            314
-------------------------------------------------------------------------------

[virtualtam]

+REST

[ArthurHoaro]

Closing due to #655