Cleanups

[podborski]

• Initial clean ups for user-defined features which are now redundant as those can be found using the presence of the 4CCs which we already parse.
• add new issue template, improve existing templates (cherry picked, merged)
• make unrecognized features fail the pipeline
• fix all user-defined features in all files
• add missing boxes

[podborski]

@DenizUgur could you take a look how to resolve the failing test. I moved out sample entries defined in ISOBMFF to codecs.json in this commit 5ef2d49, and it seems to not like it.

[DenizUgur]

This happened because in that commit you removed the only entry that listed its type as SampleEntry. I'll have to check if this error can be silenced. There is another hierarchical check for these kind of indirect type matches. Maybe this was a corner case.

{
    "fourcc": "encs",
    "description": "Encrypted Systems stream",
-   "type": "SampleEntry",
    "containers": ["stsd"],
    "syntax": "TODO: Bug. see 'rest'"
}