More graceful `@parent` directive handling [issue #4942]

[4.2] Simplifies `Factory::extendSection` method
[4.2] Removes `@parent` from content before returning from `Factory::yieldContent`
Blade @forelse
Merge pull request #4943 from jimrubenstein/patch-1

[4.2] Graceful `@parent` directive handling [#4942]
Shorten code.
Removed unused use statement
Changed @forelse syntax and allow for nesting them
Fixed view docblocks
Fixed throws docs
Fixed various docblocks
Merge pull request #5083 from GrahamCampbell/4.2-throws

[4.2] Fixed Throws Docblocks
Merge.