When managing multiple accounts it's hard to determine which one you're
currently viewing. This patch makes sidebar look like this:

+++++++++++++++++++++++++
luke@lukesmith          +
----------------------- +
INBOX                 99+
Sent Mail               +
Drafts                  +
Trash                   +
Spam			+
+++++++++++++++++++++++++

The only problem with it is the necessity of changing sidebar_format, as with
its current value these 2 excess mailboxes are being appended with 0. That
leads to situation when size of an empty mailbox is being displayed as empty
string instead of 0. I consider it's not a big deal.

This commit untracks personal.muttrc and moves the import of
personal.muttrc to the last line of muttrc. I did this for several
reasons:

1. I moved the personal.muttrc import to have the possibility to
   overwrite settings made in muttrc. This makes personalizing mutt
   easier.
2. Since personal.muttrc is currently empty, but gets automatically
   filled with the macros to switch between mail accounts, this will
   always appear as a modified file in `git status`. Also when all mail
   accounts get deleted via mutt-wizzard.sh, personal.muttrc gets
   deleted and therefore might cause inconveniences this way.
3. This makes it virtually impossible to accidentally commit personal
   mutt configurations, which would be pretty easy if personal.muttrc
   stays part of this repo as a tracked file.
4. It makes the repo look and feel nicer.