Copy the behavior of list_components in list_milestion.
list_components filter argument is now optional
Rename list_components into component_list to have more coherent names
Rename the commands in ..._attachments_... into ..._attachment_...

Because the plural mark in nosense in such commands
Addition of a method merge into the attributes that will prove useful to add or remove some cc or keywords instead of replacing them
Use default attributes
Parents should not be prepended with #
A new son tickets is defect by default
When editing a ticket, the user may precise some new attributes and a name to use as buffer.
Addition of a method to split a ticket
Addition of some methods to manipulate wiki attachment
The type of a created ticket is not necessarily defect
Addition of a command that dumps the hierarchy of son tickets recursively
Addition of a command that dumps the description of a ticket
Addition of a helper to parse a list of tickets
Addition of a _ticket_edit helper and make use of it
Addition of commands to print an attribute of a list of tickets
Parse_date uses a timedelta element instead of hardcoding it
Addition of a way to know whether a milestone is stuck
The web command now works with a list of tickets