Template improvements

[jaapio]

Just some notes from a first glance looking at the current output (I should probably open separate issues for these):

• Everything inherited from a parent class is shown in every child class.
  For individual elements it will show "Inherited from" in the side bar on the right side, but there is no ordering by child class/ parent class or a way to hide what comes from the parent in the summary.
• When something is clicked, the menu on the left folds in again. State doesn't pertain between screens. (usability)
• Multiple class level @since tags are not parsed correctly.
  Example can be seen in: build/docs/output/classes/PHPCompatibility-Sniffs-FunctionDeclarations-NewParamTypeDeclarationsSniff.html
• Class level @link tags do not show at all.
  Example can be seen in the same file as above.
• Inline {@internal .. } tags are shown in plain text.
  Example can be seen in build/docs/output/classes/PHPCompatibility-Sniffs-FunctionDeclarations-ForbiddenParameterShadowSuperGlobalsSniff.html

There will probably be more, but I should have left half an hour ago already 😅 , so don't have time at the moment for a more detailed check

Originally posted by @jrfnl in #2130 (comment)