custom resolvers enabled

See issue: https://github.com/Kdyby/Translation/issues/46

Use like this:

```yaml
services:
	-
		class: Phc\Localization\WebsiteResolver
		tags: [translation.resolver: 10]
	-
		class: Phc\Localization\WebsiteResolverLast
		tags: [translation.resolver: 20]
```

or

```yaml
translation:
	resolvers:
		- Phc\Localization\WebsiteResolverLast
		- Phc\Localization\WebsiteResolver
```

or

```yaml
services:
	- Phc\Localization\WebsiteResolverLast
	- Phc\Localization\WebsiteResolver

translation:
	resolvers:
		- @Phc\Localization\WebsiteResolverLast
		- @Phc\Localization\WebsiteResolver
```
Agree, I prefer TAG_* as well. That would be another change for another PR.