support retrieval of folder flags

[mhammond]

Do this as a keyword arg to list_folders?

[menno]

This applies to both list_folders() and select().

[menno]

Replying to menno:

Do this as a keyword arg to list_folders?

Create a select() and a list() which provide access to all available information.

list_folders() and select_folder() can call these.

[eichin]

As a motivational example - I was digging into why list_folders returns [Gmail] but select_folder can't select it (though list_sub_folders works fine on the same string) I found that if I server._imap.debug=5 and ran server.list_folders() it gets back

29:32.75 < * LIST (\Noselect \HasChildren) "/" "[Gmail]"

so either \Noselect should be exposed somehow (so the caller can actually not select it, instead of catching the exception), or perhaps _proc_folder_list should actually filter on it outright.

I don't know what more-complicated folder hierarchies look like, though; perhaps os.walk is a better (more pythonic) model for the interface here?

[menno]

select_folder updated in 4319998fc9b5