%F now shows the auth name or recepient name/address if the
message is from you.

+ Changes NewComposer to return error.
+ Add lib to handle templates using "text/template".
+ Add -T option to following commands
    - compose.
    - reply
    - forward
+ Quoted replies using templates.
+ Forwards as body using templates
+ Default templates are installed similar to filters.
+ Templates Config in aerc.conf.
    - Required templates are parsed while loading config.
+ Add aerc-templates.7 manual for using template data.

As suggested in #268, this adds a behaviour setting for
deleting message from message viewer.

This adds documentation for the config option and the command.

There is a command and config option. The criteria are a list of the
sort criterion and each can be individually reversed.

This only includes support for sorting in the maildir backend currently.
The other backends are not supported in this patch.

This adds the ability for per-account signatures in the accounts.conf
config file. The signature is added to emails in the editor at the
bottom of the email. This includes when forwarding, replying to, and
composing emails.

There are two config options: signature-file and signature-cmd. The
former allows a signature to be read from a file and the latter allows
an arbitrary command to be executed to return the signature.

The config options have been documented in aerc-config

Add an onUpdateDirs handler. This is used to invalidate the dirlist and
redraw with the correct number of recent/unread/total messages is shown.

A config option and formatting options are provided.

Signed-off-by: Wagner Riffel <wgrriffel@gmail.com>

Allows to set `ui.spinner=` to a string which is then split by
`ui.spinner-delimiter=` (Default: comma) instead of having a hard coded
animation.

This implementation doesn't use INIs capabilities to split strings as
it trims whitespaces breaking the default animation.

Signed-off-by: Paul Spooren <mail@aparcar.org>