Implement basic budget length activity

 -Implement the start-up activity for prompting a custom budget period.
 -Implement a check in case the user tries to set the end date before the
 start date.
Create a separate start-up currency list

The user will have to go through three setup stages for the app.

 - implement a separate StartUpCurrencyListActivity where the user will
   choose their initial currency
 - Connect StartUpCurrencyListActivity with StartUpBudgetLengthActivity
   when the user chooses the currency.
 - The user is now able to go back to StartUpCurrencyListActivity to
   change their choice of initial currency.
Implement layout for StartUpBudgetAmountActivity

- Implement the basic layout for StartUpBudgetAmountActivity which will be
  the third and last activity in the sequence of startUp Activities.
Change navigation in StartUpBudgetLengthActivity

 -Delete the previous page button and forward buttons. Instead use a
 single "Forward" button that has the same style as all of the buttons in
 the app.
Implement steps header in StartUp Activities

-Implement a header that shows the current step at which the user is
located at the moment in all Start Up activities.
Save the state of StartUpBudgetLengthActivity

In order for the user not to choose the dates again in case they exit out
of the activity - the activity needs to save its state.

- Save the state of StartUpBudgetLengthActivity via saving the values in
  SharePrefs.
Save state of StartUpBudgetAmountActivity

- Implement saving of the state of StartUpBudgetAmountActivity in case the
  user wants to navigate back to other start up activities.
Implement checks in StartUpBudgetAmount

-implement budget checks in startUpBudgetAmountActivity
Extract all string in start-up activities

- extract all strings in all start-up activities.
Remove start-Up budget prompts in ProgressFragment

The initial startup prompts are no longer necessary in the
ProgressFragment, because there are Start Up activities that are
implemented.

- remove the StartNormalBudgetPrompt() and startDecisionPrompt() methods
  in the ProgressFragment as they are no longer necessary.
- implement a flag to clear all of the previous off the stack in the
  StartUpBudgetAmountActivity.
Change the main budget header to implement dates

The main budget is now named custom budget due to the fact that the user
will be able to set it to a custom period.

- Show the custom budget dates in the header above it.
- Refactor the names in the progress fragment layout to custom budget
  instead of monthly budget.
Allow user to set only budget start date

This version will have a simplified version of budget settings - which
will consist of only being able to set a budget start date.

 -Change the implementation of StartUpBudgetLengthActivity, so that the
 user will only be able to set the starting date of the budget. The Budget
 will still be monthly, but it will start and end at the date that the
 user inidicated.
Implement new logic for counting budget length

Since the user will now be able to set their own budget start day - there
is a need to figure out the new length of the budget.

 -Implement SetDailyBudget method to shorten the methods in the Budget
 class.
 -Implement getBudgetLength method to shorten the methos in the Budget
 class.
Implement getExpensesBetweenDates method

- Add a method that will get expenses between two dates (dates between start
and end of the budget that is).
Delete unnecessary activity_settings layouts

The layouts were redundant as they didn't differ with screen density.
Add ability to set budget start date from settings

 -Add the ability to set budget starting date via SettingsActivity.
Implement logic for displaying monthly budget term

-Implement the logic that will change the monthly budget textview
according to it.
Implement figureOutBudgetStartEnd method

This method will figure out the start and end dates of the budget
according to the logic implemented.

-Figure out budget start and end dates according to the special logic and
put the values in SharedPrefs.
Modify and use getExpenseBetweenStartEndDates()

-Modify getExpensesBetweenStartEndDates method to use the budget start and
end dates that were saved in the figureOutBudgetStartEnd() method in
ProgressFragment.
-Refactor other methods in ExpensesDataSource to use the same columns
everywhere to avoid confusion.
-Use the getExpensesBetweenStartEndDates in the ProgressFragment to update
progress bars.
Fix up methods in Budget Class

- Fix up figureOutBudgetStartEndDate method in Budget class. The Budget
  start month and year should always be the current month and year. This
  way the logic implemented in the method will figure out on its own what
  should be they budget starting and ending dates.
- Move figureOutBudgetStartEndDate method to Budget Class as it is more
  appropriate for it to be there.
- fix up the getBudgetLength method in the Budget class to return the
  exact budget length value.