remove noise from the notification and reorganize stuff

the notifications after accept will look like that,

 * First the notification **without modifying the fields** (so only comment):

```text
#413: My title 123 - http://penelope/trac/penelope/ticket/413#comment:11

Comment (by andrzej.mleczko@redturtle.it):
This is the comment without fields modification

--
Reporter: andrzej.mleczko@redturtle.it
Owner: andrzej.mleczko@redturtle.it
Type: verification
Status: assigned
Priority: major
Milestone: Sprint 14 
Component: trac
Trac: penelope <http://penelope/trac/penelope>
```

 * Next the full notification when **modifying fields**:

```text
#413: My title 123 - http://penelope/trac/penelope/ticket/413#comment:12

Changes (by andrzej.mleczko@redturtle.it): 

 * component:  google docs => trac
 * comment:  this is the comment with component field modified

--
Reporter: andrzej.mleczko@redturtle.it
Owner: andrzej.mleczko@redturtle.it
Type: verification
Status: assigned
Priority: major
Milestone: Sprint 14 
Component: trac
Trac: penelope <http://penelope/trac/penelope>
```

 * The use case when user modifies description was removed (it generates a very confusing email)