Evolution: Add new tab for "Semantics"

THIS IS NOT A BUG, BUT AN EVOLUTION.

Add a 5th tab in ACE report, dedicated to Semantics. This would help controling the quality of epub:type and ARIA role attributes (presence and values), because they are sometimes highly missing/nonsense in the XHTML.
Such a tool would be a great help, to check the quality of semantic attributes set by our ePub subcontractors. EPub reading systems and assistive technologies could trust and use of these attributes for intelligent services to the users, and ensure a good reading experience to everybody.

The semantic report could be splitted into two parts:
A. List of deduplicated semantic attributes;
B. Table of semantic attributes occurrences.

A. LIST OF DEDUPLICATED SEMANTIC ATTRIBUTES
To give a quick overview on the semantics attributes actually used in the ePub:
- List of all deduplicated epub:type values contained in the ePub;
- List of all deduplicated ARIA role contained in the ePub (both general and DPUB ARIA roles).

B. TABLE OF SEMANTIC ATTRIBUTES OCCURRENCES
To help error detection in semantic attribute value assignements, provide a detailed and synthetic table of every attribute values, set on the same HTML element occurrences.
The table would have one line per element holding the semantic attribute(s).
The columns of the table could the following:
1. epub-type value
2. ARIA DPUB role value
3. ARIA general role value
4. HTML elt name holding the attribute(s)
5. Line number in XHTML file
6 Name of XHTML file
Nota: only 1-2 semantic attributes can be set on the same HTML element, if any. Not 3, because ARIA DPUB & general roles are mutually exclusive, by construction.