Initial commit

This is an initial commit of Srinivas Balusu's work-in-progress BookSwap
implementation, with the following modifications:
 - Added .gitignore file
 - Added NetBeans project files
 - Removed unused files
 - Removed unused routes
 - Removed customized configuration settings
 - Removed Northwestern-specific LDAP authentication
 - CodeIgniter environment is now determined by CI_ENV environment variable
Merged /images into /img
Upgraded to jQuery 1.9.1
Removed short PHP open tags
Use base_url() where appropriate
Refactored controllers

- Split Posts controller into Posts, Search, and User controllers.

- Added BS_Controller, extending CI_Controller, to encapsulate common
  controller operations.

- Reorganized routes in routes.php.
Removed My Account page
Renamed route and view for search results
Added underscores in view names
Refactored models

- Split Post_model into Post_model, Book_model, and User_model.

- Merged Account_model into User_model.

- Moved authentication procedures to User controller.
Configured autoloading for libraries and models
Removed unused methods from Search controller
Removed "name" column from users table
Refactored User_model::get_user()

- Renamed get_user() to get_users().

- get_users() now accepts an array of query conditions.
Renamed "id" column in posts table to "pid"
Replaced NetIDs in posts table with user IDs

- Renamed "seller" column to "uid".

- The "seller" column used to contain user NetIDs. The new "uid" column
  contains user IDs instead, so NetIDs are now stored only in the users
  table.
Refactored post removal

- Removed removed_posts table.
- Added "status" column to posts table (1 = Active, 0 = Deactivated).
- Refactored Post_model::remove_post() appropriately.
Refactored Post_model query methods

- Replaced get_posts_by_pid(), get_posts_by_bid(), and get_posts_by_uid()
  with get_posts(), which accepts an array of query conditions.
Refactored post updating methods

- Moved input retrieval from Post_model to Posts controller.

- Refactored Post_model::update_post() to accept an options array and
  return the number of updated posts or false on error.
Refactored Post_model:remove_post()

- Moved user-input retrieval to Posts controller.
- Refactored remove_post() to use update_post().