For code readability and maintenance

Use `%global` definition for Shellfu requires and cluster fields
according to relevancy (source vs. build).

Overview of changes:

 *  imapdomo will now override imapfilter's certificate storage

    Also added CLI option, but default value is
    $IMAPDOMO_HOME/certificates

 *  Empty action will now throe usage error

    ... instead of crashing further down the line.

 *  Path in handler error message has been fixed

 *  Codebase maintenance

Overview of changes:

 *  Fixed paths to look for handlers

 *  Fixed typo in 'die()' call

 *  Added routine debug calls

Overview of changes:

 *  Removed restriction to four valid actions

    User can now define as many actions as they want by simply adding
    handlers for them.

 *  Improved usage messages

 *  Added meaningful error messages

 *  Added arguments to show version

 *  Added 'last' branch to keep latest version

 *  Fixed and cleaned up packaging info

 *  Updated for Shellfu v0.10.*

 *  Codebase maintenance

Having just 4 valid actions (albeit they do form a meaningful workflow)
was rather historical limitation caused by author's negligence.
User should be able to define any actions they want by simply creating
handlers for them.

Later we might want to provide a guidance (template) for that, but
that's a TODO item.

Fix dependencies, use spaces instead of tabs in .spec file, rename
`imapdomo.spec` to `template.spec`, rename `imapdomo.install` to
`install`, remove unnecessary `override_dh_auto_install`, add URL to
.spec, update Summary, clean up.

Overview of changes:

 *  Simplified configuration

The host split turned to be a vast overengineering.

Overview of changes:

 *  Fixed initial errors caused bu migration from mydots
 *  Fixed packaging

We don't run .lua scripts directly; we use imapfilter which solves its
own dependencies (uses liblua5).

Overview of changes:

 *  Added everything