Correctly typed values for "empty()" values [0 | "" | false | null | ...]

[SerethiX]

Fixes #76

Proposed Changes

• add the correct types to the json when the value seems empty to php. Now you can safely set false as your active flag and can use PHP 7.1 scalar type hints on the receiving side
• extended tests to cover the new type conversions
  • SqlQueryTest
  • ValueTest
• fixed a small issue where the update statement and insert statement would have different types. trim order changed
• Fixed extends of TestCases to work with the default installation via make. Got ClassNotFound Exceptions during testing

[TobiasHauck]

if (is_int($param) || is_float($param)) return $param;
if (is_numeric($param))                 return (float) $param;
if (is_string($param))                  return '\'' . $param . '\'';
if ($param === true)                    return 'true';
if ($param === false)                   return 'false';
if ($param === null)                    return 'null';

throw new \Circle\DoctrineRestDriver\Validation\Exceptions\InvalidTypeException('string | int | float | bool | null', '$param', $param);

[TobiasHauck]

Hi Nils, thank you for your tremendous work! You fixed a lot of really ugly stuff in a very clear and structured way!

May you be so kind and fix these 2 coding style issues I reported via code review? Afterwards this PR is ready to merge. Thanks once again ;)

[SerethiX]

Sure, I added another commit.