Cleaned up version of IMAP ID command
Add IMAP special_folders method to simplify Drafts folder identification
Add IMAP uid2msgid to get Gmail web message id from the IMAP id
Clean up the try blocks for sending messages via IMAP
Refactor IMAP attachment creation to another method
Make the low-level IMAP class Gmail-specific
Move the IMAP form_message out of init to a separate method call

This prepares the IMAP class for supporting a needs_imap() call
Move has_attachment() to needs_imap() in IMAP class
Pare down handled Exceptions for IMAP operations
gnomegmail.glade: Hand edit for GTK3 compatibility

The file, created for GTK2, would not load into glade 3. I made hand
edits per

   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=651264#5

to make it open correctly. This commit contains those changes.
gnomegmail.glade: Glade makes the file its own

This is the result of saving the old glade file out from the glade
3.18.3 app.
Query user for from address on every run

Using GTK3.
gnome-gmail: Change support URL to github

From the previous sourceforge url:

http://sourceforge.net/tracker/?group_id=277145
Hack out gnome-gmail gtk2 till simple url runs

Non-IMAP old-style URLs are successfully running, after the user
is queried for a from address.
Add a new ConfigParser to persist the last From:

Store non-secret configuration information under ~/.config, replacing the
old gconf storage.
Modify the simple and 'no address' URLs to use user

Use the from address provided by the user, to open the GMail page
appropriate for that user. Uses the technique introduced in:

https://github.com/ashchan/gmail-notifr/issues/37

IMAP does not work yet.