Implement changes found in 'dev' and '2.0' branches

[IQAndreas]

dev is a "parent" of 2.0 with only a two commits apart, so it's really only the latter we need to concern ourselves with.

It seems like the brunt of the changes* are renaming packages. I believe it would be convenient to slip these changes in at the same time as the Flixel v2.57 renames are taking place.

* ...that sounds wrong; I think I'm mixing up two different expressions, but I can't figure out how it's supposed to be.

[IQAndreas]

Changes in 2.0:

• Move everything from org.flixel.plugin.photonstorm to photonstorm.flixelpowertools
• Rename FX package to fx
• Rename API package to api
• Split FlxVelocity into FlxMotion and FlxDistance
• Several minor class moves (too lazy to detail)

The following new classes have been added

• Looked like there were some, but turns out there were none.

The following classes have been deleted - not sure why...

• gui.FlxButtonPlus

The following classes have been added, but are just empty - I'm assuming he was planning to fill them in future versions

• api.FlxGenericAPI
• api.FlxMochiMedia
• api.FlxNewgrounds

[Dovyski]

I'm ok with those changes.

[IQAndreas]

I'm ok with those changes.

I'd probably leave out the deletion of FlxButtonPlus unless anyone can give a reason why it was deleted (could have also been an oversight when the classes were moved around?) as well as leave out the "empty" api classes.

[Dovyski]

I've read somewhere that FlxButtonPlus was buggy and it should be removed or deeply refactored. I can't remember where I read that though...

[IQAndreas]

In the discussion on folder structure on FlixelCommunity/flixel, we are looking into creating the effects package.

Shall we rename the fx package to match Flixel, naming it effects as well?

[Dovyski]

Yeah, I think that's a good idea to keep things uniform.

[VestOfHolding]

I was having issues with FlxButtonPlus in my project, but nothing that would give reason to just delete it. For example, I wanted to be able to change the color of the text using another parameter in the constructor, but that turned out to be more frustrating than it was worth at the time. Even if it needs tweaking, the class is solid.

[Dovyski]

I think we should merge FlxButtonPlus with FlxButton following the same procedure we are using to merge the rest of Flixel Power Tools.