Introduce user_has_cap filter

[moorscode]

When we use the user_has_cap filter to add the "sub" level capabilities (anything other than wpseo_manage_options) when the user has the wpseo_manage_options capability, we can throw away the WPSEO_Capability_Utils and just use the current_user_can function to handle all capabilities.

When removing the WPSEO_Capability_Utils from the code, also make sure these are removed in Premium.

Example code for wpseo_manage_redirects can be found in the following commit:
https://github.com/Yoast/wordpress-seo-premium/pull/1386/commits/d6f509f50c692ac2320666d7eab17ece4f0bf77f

[atimmer]

Consider using map_meta_cap. This is the way WordPress map different capabilities onto eachother.