Allow use of a configuration file `.beerc` comparable to `.drushrc`.

[MegaphoneJon]

Zulip discussion is here.

An initial focus would be on implementing global options.

Like .drushrc, bee should check for .beerc in several locations and concatenate the values, using a (documented) order of precedence.

Here is the order of precedence for `.drushrc:

• 1. Drupal site folder (e.g. sites/{default|example.com}/drushrc.php).
• 2. Drupal sites/all/drush folder.
• 3. In any location, as specified by the --config (-c) option.
• 4. User's .drush folder (i.e. ~/.drush/drushrc.php).
• 5. System wide configuration folder (e.g. /etc/drush/drushrc.php).
• 6. Drush installation folder.

example.drushrc is here for reference.

[yorkshire-pudding]

In #458 I added a default terminal width if tput cols fails to get the terminal width. This (i.e. $options['default-terminal-width']) would be a good candidate to include in an options file; it has less value as a standalone global option entered with each relevant command.