Add Support for Storing Values as Strings in the Database

[bltravis]

This will add the ability to specify (at runtime) whether you would like to save MACs as strings (varchar) or integers (bigint) via an "integer" keyword (defaults to True, i.e. existing behavior). I've also reworked how to specify a default dialect (via a settings variable and a utility function that handles importing it), and added a function to format any given EUI instance via a specified mac_eui48 subclass. I know that my change to how a default dialect is set is backwards-incompatible, but I think it's more elegant solution than using a class method.

[kra3]

I'll have a look in this week & Thanks for keeping mac address in strings. (which will help in more easy searching.)
I believe it's done on top of latest release of this repo and String mode doesn't break Admin Search.

Also, I've to check anyone who might have using MACAddressField.set_dialect isn't left behind.

[bltravis]

I'm going to have a crack at adding support for the select_dialect class method (with a deprecation warning of future removal (v1.4?)) and I'll push that to my repo when it's done, and get it added to this pull request.

[bltravis]

And, there it is. That last commit should re-enable the existing set_dialect class method, and adds a deprecation warning that the feature will be removed in the next release. The warning is issued whenever the field class is first called, and the first time default_dialect returns MACAddressField.dialect. By default, MACAddressField.dialect is now None, and my original default behavior for default_dialect is followed (settings-supplied class or mac_linux). If set_dialect is used, then default_dialect returns that value.

[bltravis]

Went ahead and merged in this repository's master into mine to make merging this request easier.

[kra3]

Thanks a lot @bltravis for your support and passion. 👍
I'm travelling today, so will be merging the change sets probably by tomorrow or day after that.
Hope you can wait till then

[bltravis]

Merged from upstream to make it easy to merge into the main repository.

[kra3]

Done & Thanks :)