wish: affectation UX: when creating an auto affectation, add a "test your rule" button

[HelloTheWorld]

easy to explain, may be hard to code :

When modifying / creating an auto assignment rule, to check if it works, you have to :
1 - save your rule
2 - exit assignment window
3 - go to / open your account where it shall modify something
optional : filter your operation to show operation that shall be modified
4 - go to menu "apply auto rules"
5 - check if it worked
...If not,
6 - go back to main window
7 - open menu to modify auto affectation
8 - open affectation to modify
9 - THEN you can debug.

MY WISH :
remove most on those steps by adding a "Test my rule" button in the modification window, showing :
- (easy option) popup window "X operations complies in Y accounts", or
- (hurt me plenty option) "here is the detailed table of what operations comply to this rule in what account".

For me, the easy option shall be enough to check if I forget something in the rule parameters.

ATTACHMENT:
Example of button "TEST this rule !" in attachment

[HelloTheWorld (loic-dupont)]

TO correlate with : https://bugs.launchpad.net/homebank/+bug/2042038