[5.6] Allow using Blade @json statement with arrays or method calls

[imbrish]

Introduction

Currently @json won't be compiled correctly if used with anything else than simple values or variables.

This PR allows following:

@json(["foo" => "bar", "abc", 12.34, [1, 2, false]])
@json(Foo::bar("abc", 12.34), JSON_HEX_TAG, 256)

Backward Compatibility

Above examples would previously result in either syntax errors or calling json_encode with incorrect options or depth. Nothing that worked before should break. If you however can think about some odd edge-case that will break I'll be glad to take a look!

Details

I added new BladeCompiler::parseArguments($expression) method, which uses regex to split arguments list given as a string into a flat array. It's rather forgiving and won't complain about syntax errors.
This could lead to some non apparent issues when malformed arguments are used. However I decided not to fight an uphill battle and bet for simplicity instead.

If you're inclined to merge this I can add some tests for that method. It could be reused in other compile* methods or when defining custom directives.

[taylorotwell]

I don't feel like maintaining and debugging that regex. Sorry.