Add option to set bundled variations instead of using the default variation

[evertiro]

Copied from https://github.com/easydigitaldownloads/EDD-Software-Licensing/issues/788:

Overview:

We sell bundles on both our websites: WordImpress.com and Givewp.com - the bundles on wordimpress have the following variables:

• 1 site
• 5 sites
• 15 sites

  Bundle screenshots:

Download screenshot:

Problem

If I purchase a 5 site bundle from either site the licenses appear to be created properly in the back, but when I view the purchase confirmation and email receipt there are mixed license counts:

These should all be "Up to 5 Sites":

These should all be "Up to 5 Sites":

In the backend it appears fine:

---

This is confusing to our customers and causing them to be frustrated when they purchase a certain license and discover we are giving them false information. A few have forwarded their emails and we've had to honor their requests to bump their license counts up for free.

[evertiro]

I just realized that this issue was opened on the wrong repository. The user who opened it assumed it was an SL issue because of the licensing aspect, but the actual problem (as eventually confirmed by the user) actually has to do with how bundles are created. Bundles should allow selecting which item in a variably priced product is included, but right now just enforce whatever the first option is.

[pippinsplugins]

This will be doable once #3175 is done (I think).

[michaelbeil]

I have seen this on one other site. Both sites have a high customer base so we should look into getting this fixed sooner than later.

[michaelbeil]

Here is a reference to another ticket: https://secure.helpscout.net/conversation/263336215/44627/?folderId=725711

Also, @pippinsplugins, seeing that https://github.com/easydigitaldownloads/easy-digital-downloads/issues/3175 was done in 2.6.9, how should we milestone this?

[pippinsplugins]

Let's aim for 2.8.