Fix layout of activity_add_task.xml

1. The layout of activity_add_task.xml no longer has elements floating
   over each other. The layout has also been converted to a ScrollView.
2. Task priority is now saved at task creation.
3. Fixed a bug where blank task notes would wreck the data storage
   file. Now the code checks for whether or not the notes are blank.
4. Cleaned up formatting and comments of AddTaskActivity. The first of
   many.
5. Added initial JavaDoc to the repository (doc folder), though at this
   point it is 95% auto-generated.
Create new package "comparator".

1. TaskCompletionComparator moved to comparator package.
2. TaskPriority renamed to TaskPriorityComparator and moved to
   comparator package.
3. Non-comparator elements of TaskPriorityComparator class moved into
   Task class.
4. All the current Java source files now have correctly formatted JavaDoc
   comments. The doc folder has been updated.
Change app name

1. App name is now "Task Butler"
2. Updated copyright notices in each source file
Add long click to tasks in main activity

* Long clicking a task in the main activity pops up a context menu.
* There are 2 options: edit (unimplemented) and delete.
* Delete pops up an alert dialogue to confirm the deletion, and deletes
  if confirmed.
Add creation date and due date to tasks

* Tasks now have creation date and due date fields (calendar objects)
* Changed setter methods to allow method chaining
* Removed all assignments from Task constructor because it was getting
  unwieldy. Field assignment is now done exclusively through setter
  methods
* Added task comparators as fields to the TaskList class
* Overhauled how notes are saved to file. It is similar to the new
  implementation of how calendar objects are saved to file. This method
  will be used for any additional "optional" fields in the future.
Add due date to new tasks

* New tasks now have due dates attached. For now this is mandatory but
  it will eventually be optional
* Updated how tasks are displayed in the task list in the main activity
Add new Task comparators

* 3 new comparators: compare by date created, date due, and name
* Added user permission requirement RECEIVE_BOOT_COMPLETED to manifest
  in anticipation of implementing background service on startup
* Updated /doc to latest Javadoc
Add ActionBarSherlock as library to project

ActionBarSherlock will give full action bar support to the app.
Normally the action bar is only supported in Android 3.0+, but with
this library our app, with min SDK 2.2, will be able to have action
bars.
Update readme
Update theme to Theme.Sherlock
Remove context menu from MainActivity

* Context menus are being scrapped in favor of contextual action modes
  using the ActionBarSherlock library
* Updated comments in all Java files to make classes easier to navigate
Add contextual action mode to MainActivity

Long pressing a task in the list will pop up a contextual action mode
allowing the user to edit or delete that task. Deletion works, but
editing is not yet implemented.
Add action bars to MainActivity and AddTaskActivity

Action bars are now being used for app navigation instead of buttons,
and icons instead of text. The result is a much cleaner interface.
Change format of action bar icons
Add sort submenu to MainActivity

* Sorting functionality is still not implemented, but the front end is
  mostly finished
* Standardized naming of resource IDs to type_activity_name in order to
  prevent conflicts later
Start work on SettingsActivity
Add delete menus to MainActivity.

* Two new deletion options: Delete completed and delete all
* Alert dialogs ask the user for confirmation and warn that the changes
  are permanent
Implement auto-sort

When auto sorting is selected in the drop-down menu, the task list is
sorted by completion status, due date, urgency, and name.
Remove TaskList.java

TaskList never became what it was supposed to be. Most of its intended
functionality was implemented in TaskListAdapter. So in interest of
keeping the code clean, it was removed and Tasks are now collected in a
simple ArrayList.
Change task list modification

Modifying the task list is now exclusively done through the
TaskListAdapter API. Previously, it was a mix of ArrayList and
TaskListAdapter calls which was messy and potentially going to lead to
problems.