Accessability

This pull addresses many/most of the accessibility concerns raised at WeBWorK::Portland.  I've gone through the changes and listed them below.  By and large they can be tested by just looking for them on a test course.  Some other things one could do to test are to check the page with Wave or to use a screen reader.   There may still be some issues on instructor only views.  
-  added upgrade_admin_db.pl script to bin and added a warning to database errors that look like they are coming from missing columns.  Test by downloading this pull and trying to log into the admin page.  Then try to run the upgrade_admin_db.pl script. 
-  upgraded MathView to be more accessible.  You should test by using tab and enter to navigate around the a MathView menu.  Its a little cumbersome, but it should more or less work. 
-  I'm using Davide's changes to color.js and I changed the way it colors correct/incorrect problems to be more of a glow rather than a background color
-  I darkened the light blue buttons and generally tweaked colors.  All of the new colors should meet AA standards, although its possible I missed some alert coloring or things like that.  These new colors should also be in the override file.  
-  I added a yellow focus box to make focus more clear for links.  
-  I redid the Gateway results table to look more like the table on the Problem page.  The issue was that the old table was a mix between a layout table and a data table. This one is just a data table.  It should be check in math3 and math4
-  The Gateway problem labels are now headers and I changed the "Preview Problem" text to "Preview Answers"
-  I replaced the download radio buttons on the student ProblemSets page with download links.  The links are icons and on math4 they have hidden screen reader text.  They shouldn't appear for open sets. This should be checked in math3 as well
-  All pages should have a "skip to main content" link now. It should be hidden until it is selected with tab. 
-  I added a red * next to required form fields.  This is a little tricky because some form fields are not required in the technical sense, but it would be silly to not include them.  I generally only included a * if the system would give an error.  
-  The toggle sidebar button now has hidden text to go with the icon for screen readers.  (All icons should now have this).  The text should change when the icon changes. 
-  The main menu text in the side navigation bar should be a heading and in general there should be enough headings to navigate around the page. 
-  I removed the Options menu from the side bar and put it into the Password/Email page, which is now User Settings
  -  You will need to upgrade your course tables because of this. 
  -  You should check that you can change your settings in the User Settings page and that those settings are used on the pages which respect them (GatewayQuiz, Problem, ProblemGrader is all I know of)  
  -  The options should respect the existing permissions and settings. (E.G. they should turn off if you aren't using, say, MathView)
-  All input fields should have a label (except for answer input fields)
-  I redid the grades table (this redoes the table in Grades, as well as the tables for individual students in Student Progress and Statistics.  The main thing I did was to break up the "pre" formatted string into different columns.  This should be checked in math4 and math3.  (I also added the "highlighting" from the StudentProgress set view).  
-  I changed Show Past Answers so that * also works with number ranges and blank entries are interpreted as *.  I also fixed a bug where using * for a sets would give up once it found a set it couldn't do.  Test by using * in the set field on a user which is not assigned to one set or another.  I also changed it so * shows all gateway versions by default.  
-  The "incorrect"/"correct" lines in the results table are now links that change focus to the appropriate input field.  (Thanks Jason.) 
-  Other small changes include adding the date to the ProblemSet title, changing the wording on the problem page to "show correct answer column" and "Preview My Answers", as well as the navigation labels.