C++ 17 Specification support

[zelenyhleb]

After some experiments on the cpp17 specification standarts I have some interesting results:

JTidy ignores empty tags by default

Already fixed it in branch.

Some points are duplicated #152

This speccification requires to change naming conventions a bit, because some point names and descriptions are duplicated, while their contents doesn't.

Table list resolution#151

Tables cannot be added to model because of OOB Exception. Needs further investigation.

Parsing synopses #163

Just crashes on parsing synopses. Can't find <code> element, as I assume according to the error. Commented creating synopses for now.

Spot crashes #151

Some tables cannot be parsed for unknown reason. RGM crashes on title resolution (out of bounds).

Cpp revision selection #153

We need to let user choose which specification he wants to import and introduce some UI for it.

Ensure TOC is parsed correctly #157

We need to ensure that TOC structure is parsed correctly for CPP 17 as well.

Ensure sections structure is parsed correctly #158

We need to ensure that sections structure is parsed correctly for CPP 17 as well.

Ensure References are correctly set #159

We need to ensure that in-point references are set correctly for CPP 17 as well.