Move initialisations to declaration for smaller PPS related classes. Define empty
constructors/destructors in header.

- move VPS and related classes into VideoParameterSet.h/cpp
- move SPS and related classes into SequenceParameterSet.h/cpp
- move PPS and related classes into PictureParameterSet.h/cpp
- rename ProfileLevelTier.h/cpp to ProfileTierLevel.h/cpp and move ProfileTierLevel class there

No other changes except for minor formatting/comment cleanup

Keep original extractPTLInformation() method to minimize changes accross repo

Get PTL from VPS in case of Multi-layer OLS.

Refactor ProfileLevelTierFeatures::extractPTLInformation to accept PTL
from VPS, not only from SPS.

When vps_pt_present_flag[i] == 0, infer Profile, Tier and constraint
info for i-th PTL to be the same as that for (i-1)-th PTL.

for this condition in encoder.

m_pProfile is a nullptr in that case

In encoder, when automatically selecting profile, choose a still
picture profile when the level is 15.5 and a single picture is to
be encoded.
In decoder, don't check for single picture constraint when looking
up profiles.

Align software with specification fix #1247

CPB changes impact 8K levels; MinCRScaleFactor for 4:4:4 profile.

Renumbering level according to major*16+minor*3, with maximum level now
15.5 (not 8.3).