MDL-46950 gradereport_grader: Consolidate styling of the elements

The grader table has been made entirely standalone from core or
theme styling. The floating divs have to share the exact same
rules, and so it was a lot easier and more maintainable to just
style them both using the same selectors, entirely ignoring the
table default styles.

And because the selectors are unique for both the floating elements
and the table cells, a themer can easily re-use them to style both,
without having to dig around to find all the selectors to overwrite.

Working on this highlighted some issues with the positioning. Those
have been fixed within the same patch. And even though it is still
not 100% correct on IE, the result is pretty decent.

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-46950 gradereport_grader: Prettier styling for base and clean

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-46988 gradereport_grader: Fix styling issues for RTL

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-47027 gradereport_grader: Styling when editing is turned on

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-47027 gradereport_grader: Removed floating save changes button

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-47053 gradereport_grader: Add a floating Footer Title cell

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-47025 gradereport_grader: Removing highlight feature

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-47026 gradereport_grader: Removing the tooltips

They are not serving the same purpose as the one they had before,
and they were overlapping with the content of the cell. Positioning
them somewhere else made them more confusing than helpful.

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-47063 gradereport_grader: Styles applied for overridden grades
MDL-47028 gradereport_grader: Add floating headers for other cells.

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-46936 gradereport_grader: Restore AJAX editing to gradereport

Removed id argument from AJAX code, no longer supplied.

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-47124 gradereport_grader: Update row/column sizes when showing/hiding quickedit fields

This makes use of Global YUI events to trigger the resized event handler.

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-46658 gradereport_grader: Make page CSS more specific
MDL-47353 gradereport_grader: Fix header offset logic for floating headers

This is necessary for themes with non-fixed navbars to work with the
grader report, otherwise headers will be hidden.

This issue is a part of the MDL-46658 Task.
This issue is a part of the MDL-25544 Epic.
MDL-44536 workshop: Fix missing phpDoc for user report callbacks
MDL-31936 workshop: Initial implementation of the course reset support
MDL-47299 libraries: upgrade PHPMailer to 5.2.8
MDL-31936 workshop: Add unit tests for the workshop reset
MDL-31936 course: Add missing file level docblock to the reset_form.php

Not related to the issue itself but spotted while working on the
workshop reset feature.  Assigning copyleft holder to Petr as the
original author of the file.
MDL-31936 workshop: Fix overall feedback content processing order

This is unrelated to the issue but was spotted while testing it. The order of
format_text() and file_rewrite_pluginfile_urls() was incorrect and threw
debugging message. Fixed now.