Improve generated javadoc and zipfile

Add a better copyright notice to the footer of javadoc (include the
magical &copy; symbol, and the current year 2013).

Add the user-visible bits of the iOS and GWT backends to the javadoc
construction.

Change the version number to "0.9.9-SNAPSHOT", as I believe this is
where libGDX is.
Add 'includeantruntime="false"' to javac

Newer versions of ANT warn about the fact that the ANT runtime is
included on a javac compile.  Since this is not generally what is
wanted (but is backwards compatible with older versions of ANT), a new
flag
	includeantruntime="false"
will disable it.

This will clear up the Jenkins warnings like this:

    [javac] /var/lib/jenkins/workspace/libgdx/build-template.xml:51: warning: 'includeantruntime' was not set, defaulting to build.sysclasspath=last; set to false for repeatable builds

AFAICT, this is backwards compatible with older versions of ANT ...
Copy libgdx.so too

Need to manually copy libgdx.so into ${distDir} too.  This should
probably be some sort of glob like "**/*.so"?
Copy downloaded ARM libs into gdx/dist/armeabi*

Need to populate gdx/dist with the libraries that the native build
would've created.  (Maybe?)
Update README.md

Add the 'ant -f fetch.xml' step.  Add a bit more text about building
in general.
Hack to add missing libs directories on demand

This really can't be right, can it?
Switch to cleaner mkdir

Do ${libs} mkdir at 'clean' time, not 'init' time
Improve compilaiton instructions

Explicitly point out the three ways to build libGDX, describe each
quickly and point off to the documentation for each.