Extend price set for contributions

To add the price sets to online/offline contributions

1. Schema Changes
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• Add a new column "extends" to the `civicrm_price_set` table so which stores the price sets on events, contribution/contribution pages, and gives an option to choose which price sets show where.

2. User Interface Changes
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2.1 Events >> New Price Set

• Add checkbox form field to "New Price Set" form named "Used For" with options Events, Contributions
• Allow a configuration option in Contribution Page to choose from the list of price sets that have been configured for "Contributions", same goes for events.
• Allow unchecking any option in "Used For" as long as it has NOT been used in a transaction

2.2 Manage Contribution Pages >> Configure >> Contribution Amounts

• Add drop down form field to this form below the "Pay later option" field.

• Price Set (with all the options that have been configured with Used For = 'Contribution' checkbox above)

• Choosing any price set should supress all the form field below.
• Add form rule to NOT allow using this feature with "membership".
• Contribution test/live pages should reflect the configured price set and should should show line items table for price sets on Confirm & Thank You pages similar to event registration.

2.3 New Contribution

• Add mode, on "Total Amount" field, give the list of price sets configured for Contributions (if any), on choosing which it should supress the amount text and replace with the chosen price set and should allow to switch back and forth from price set back to text.
• Update mode, it should show the "line items" table to show fill fields of price set were filled/ selected/checked.

Changes to current work flow:

We should create line items for all the transactions live/test/ online /offline.