Support align and min_width module options

Support align and min_width module options

This patch enables users to define "align" and "min_width" options
right in the i3status module config sections.

Specifically this patch:
 * Adds macros for the two new options that are used in the option
   definitions. As the min_width option can take either a string or a
   number, a custom type has been added along with a corresponding callback
   function that parses the provided value (and provides input validation).
   The align option also uses a callback for input validation
 * Expands all module config option definitions to include the new
   options
 * Extends the SEC_CLOSE_MAP() macro to generate the JSON for the new
   options as necessary
 * Updates the manpage to explain the new options