optimized apply() by moving $operators into a static array where possible

[tapsavo]

Moved most of $operators -array's content into a static variable, so the array doesn't need to be defined on each call to apply().

Operators for var, missing and missing_some were crudely moved into the if/elseif/else structure as those needed use ($data). Their implementation in the if/elseif/else could probably be prettier.

Rationale for this change was performance. In our application we needed to run n-amounts of apply() calls to potentially thousands, sometimes tens of thousands of arrays, and it quickly became apparent that there was some room for optimization. After moving the $operators as static, the apply() -calls only used 1/3rd of the time they used to.

In my (crude) tests, with 100k loops for these test logics and data

$loops = 100000;
$logics = [
    [
        "and" => [
            ['var' => 'dummy'],
        ]
    ],
    [
        "and" => [
            ['var' => 'foo'],
            ['var' => 'foo']
        ]
    ],
    [
        '+' => [
            ['var' => 'foo'],
            ['var' => 'foo']
        ]
    ],
    [
        'missing' => 'foo'
    ]
];
$data   = [
    'foo'   => 11,
    'bar'   => 127,
    'dummy' => 'foobar'
];

$org_start = microtime(true);
for($i = 0; $i <= $loops; $i++)
{
    foreach($logics as $logic)
    {
        \JWadhams\JsonLogic::apply($logic, $data);
    }
}
$org_end = microtime(true) - $org_start;

$opt_start = microtime(true);
for($i = 0; $i <= $loops; $i++)
{
    foreach($logics as $logic)
    {
        \JSLOma::apply($logic, $data);
    }
}
$opt_end = microtime(true) - $opt_start;

var_export([
    'jsl' => $org_end,
    'oma' => $opt_end,
]);

array (
  'jsl' => 1.6032569408416748,
  'oma' => 0.42403507232666016,
)

The "static operations" version performed in 1/4th of the time the current 1.5.1 version does. This was with opcache enabled on php.