tigefa4u projects Trac

Merge changes from trunk: 5171,5173-5178,5182-5197

More #5099 fixes, this time about ticket comments.

Ticket object model is more robust when looking up a field value. This is useful when requesting a value for a custom field on a ticket that has been created ''before'' that custom field has been added. Related to #5099, but this has use-cases besides the templates, that's why the fix has not been done at the template level.

Fix display of tickets when they contain values for custom fields which are no longer in use. Related to #5099.

Custom query accept dynamic variable. This is a more genericimplementation than r3999. Closes again #1467.

Fixes #5095: Add 'delete query' button.

Fixed small issues with Genshi trunk (see #5099). This concerns:
- wiki preview
- attachment rendering
- new milestone

Fix a few diff related template errors (see #5099)

Genshi trunk compat: setup ''title'' template variable for internal errors

Don't raise an internal error when granting an already granted permission or when adding a subject to a group when it was already part of that group. Fixes #3873.