Administration: Move more table strings to sentence casing.

WordPress as a project has moved largely to sentence casing for UI elements in the admin. This commit moves several string$

* Move to trash
* Mark as spam
* Permanently delete comment
* Approve comment
* In response to
* Bulk actions
* Not spam
* Sumitted on
* Delete permanently
* Add media
* Upload files
* Upload images
* Add media
* Bulk select
* Restore from trash
* Search media
* Attachment details
* Create gallery
* Edit gallery
* Cancel gallery
* Add to gallery
* Image details
* Replace image
* Cancel edit
* Edit image
* Choose image
* Select and crop
* Skip cropping
* Crop image
* Audio details
* Replace audio
* Add audio source
* Video details
* Replace video
* Add video source
* Select poster image
* Add subtitles
* Create audio playlist
* Edit audio playlist.
* Cancel audio playlist
* Create video playlist
* Edit video playlist
* Add to video playlist
* Filter media


Fixes #40244.
Props afercia, bhargavbhandari90, rcutmore, webzunft, manojlovic, jeremyfelt, desrosj, lschuyler, SergeyBiryukov, whyisjake. 


Built from https://develop.svn.wordpress.org/trunk@48352


git-svn-id: https://core.svn.wordpress.org/trunk@48121 1a063a9b-81f0-0310-95a4-ce76da25c4cd