Configuration file

[John Goerzen <jgoerzen@xxxxxxxxxxxx>]

OK,

Martijn raised a good point -- where to go with the config file?

Right now, we have a config file format with three sections in addition to
account names:

 * general
 * mbnames
 * ui.Tk.Blinkenlights

While this is following a consistent scheme ("general" for overall settings,
all others with the Python name of their module, without leading
"offlineimap."), it might not be best, and with no effective restructions on
account names, each time a new section is added, we have to be concerned
about collisions.  It's not just limited to account names with periods
either -- there are other top-level modules threadutil, version, imaputil,
imapserver, and imaplib that might someday want to have a config section.

In OfflineIMAP 3.2.0, I added a change to reject account names containing
periods, but Martijn rightly pointed out that this is not a good change (at
this time, at least).  In the past, I have made an effort to restrict
non-backwards-compatible config file changes to only major releases (ie,
4.0.0).

Comments?

-- John