Fixes a bug whereby the comments in green lines are not displayed.

solves pepegar/trac-code-comments-plugin#2.
Minor changes to avoid changing the value of CodeComments.path.

Used a third argument "file" in the call of AddCommentDialog.open() that contains the
filename of the file we are commenting on, so we can still have a path without changing
any of the properties of CodeComments.
Updated the upgrade process

creates the new column and converts the old comments to the new schema.
Changed the sql statement to query only the mandatory fields
Refactorized the views to try to avoid conditionals with CodeComments.page as much as possible.
typo
Shows the changeset comments in the file screen.
Reverted the changes in the last commit.

Changeset comments in the browser doesn't make sense.
fixed bug where not all changeset paths were being matched
typo fix (arrachments->attachments)
Fix "undefined" filename when commenting on a changeset
Fix line numbering display issues when commenting on a line of a changeset

To associate a comment with a specific line of the changeset, we use the row number in the diff table displayed by Trac.  However, this didn't work for diffs with multiple files (if the first file had five lines, the second file's first line would be line #6) or deleted lines.

I added a displayLine variable that controls what we show to the user: the actual line number of the file, or its former line number if the line was deleted.  (We still use the absolute row number to store the comment, since otherwise we couldn't disambiguate which line the comment belongs to.)
Fix "Path" display in Code Comments table for changeset comments

Be more specific about when a comment is on a changeset vs. a file.  Also, remove the line number from the changeset for now, because it's confusing (it refers to the absolute line number of the changeset, NOT the line within the file).  To show that a comment refers to a particular line in a changeset, we add "(in filename)".
Get rid of the "is" option in attachment_info
Initialize comment path to empty

This fixes the "Comment instance has no attribute 'path'" error that prevented comments from being added to changesets, or in reply to line comments on changesets.
Only use displayLine if we're looking at a changeset

Doing this for files occasionally leads to accidentally using the contents of the line as the line number.
First hack at fixing mouseover issues on changeset lines

This at least keeps the line height the same (though at the expense of the icon) and properly hides/shows the line content.
Use text().trim() instead of innerHTML to test for empty cell contents

This fixes a bug where the mouseover wouldn't properly detect a deleted line the second time (due to the existence of the 'toggle' span)
Use a separate callback function for changeset line comments

This is better than littering a single callback function with conditionals.
Add toggle spans to all TH elements on render

For hiding the cell content on mouseover, it's cleaner to do this once on render than have to check to see if the span is there every time.