Core: ICS-127 Add the module and rename it to imagex_alphabetical_sitemap.

## Ready State: Yes

This pull request is related to the following JIRA tickets: [ICS-127](https://imagex.atlassian.net/browse/[ICS-127]).

Also adds general description and roadmap to README.

## Requirements & Dependencies

* ctools
* entity
* fuzzysearch
* history_js
* search_api
* search_api_db
* search_api_views
* views

## Deployment Instructions

* Merge code.
* Install and enable dependencies
* Enable module `imagex_alphabetical_sitemap`: `drush en imagex_alphabetical_sitemap`
* Clear caches with `drush cache-clear all`

## Usage/Test Instructions

* Browse to admin config form and verify default settings /admin/config/search/alphabetical_sitemap
* Setup search index and make sure index is populated
* Inspect view and ensure it's pulling content you want included in the UI
* Browse to page defined in admin ui and verify functionality
* Create your own feature module to contain your site specific settings that deviate from the defaults