AccountType: Add instructions for implementors to javadoc
AccountType: Change createAccount signature - accept Activity as an argument - Facebook accounts need this in order to create account
AccountType: Expand TODO comment for logo
Account: Make accountType private - don't want subclasses modifying accidentally
Account: Add protected constructor with AccountType as parameter - every subclass must initialize this field
Add initial support for Facebook accounts
AccountManager: Add proper javadoc
NewAccountTypeSelectActivity.onListItemClick: Remove javadoc. Rename parameters. Remove code for creating account, needs to be revamped.
AccountManager: Remove field availableAccountTypes
AccountManager: Add private field availableAccountTypes, and add a getter for it as well. This replaces earlier field with same name.
AccountManager: Remove method getAccountType. Make class a singleton, accessible through getInstance.