Analyse and implement some extra checks about phpdoc blocks spacing and tags groups

[stronk7]

This comes from #134, where it was detected that a few (minor) style details are not being checked currently. Here it's an initial list, to be discussed, analysed...

• Blank line between summary (short desc) and description (and for which artifacts).
• Blank like between descriptions and tags.
• Maybe some ordering and spacing between tag "groups" (copyright, author, license => params => return => other tags)
• ....

(As reference, when not specified by our own coding style, we should follow the PSR-5: PHPDoc draft.

Ciao :-)