RFC Batch modals comply with the new layout

[dgrammatiko]

Batch modals are hardcoded. This is a proposal to make them more flexible/overridable. Right now it’s only for banners, but, if this gets some attention I will make it site wide.

So what’s in it?

Well batch modals have a tmpl/default_batch.php file that holds all the html code for the modal.
But since @smz and @phproberto made some nice changes in the bootstrap modal everything is more modular and everything is controlled from the respected layouts e.g. body, footer.
So this PR tries to break the hardcoded html code to 2 files tmpl/default_batch_body.php and tmpl/default_batch_footer.php
Now we have more control over the output (read this as getting ready for bs3)

[ghost]

@test

Template Isis Success with current Firefox, IE11, current Chrome. and com_banners.
Batched several items succesfully. Could cancel, close etc.

Template Hathor: Error 500 Layout default_batch not found.

[Kubik-Rubik]

@test Tested successfully with both administrator templates. Batch feature still works properly!

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[MATsxm]

@test

#7000 Tested successfully with both administrator templates.

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[smz]

@test OK (both admin templates)

@dgt41
I think it is not necessary to set the width and height parameters options for the modal: if I remember correctly those are used only in case of an iframe modal, which is not the case here...

[Kubik-Rubik]

@smz Sergio, if you test it, then please mark your result in the issue tracker as well (not only in a comment at GitHub).

@dgt41 Thank you for your contribution. I will merge it!

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[smz]

@Kubik-Rubik ... oops, forgot about it, sorry!

[Kubik-Rubik]

@smz Sergio, no problem at all, just a small reminder! :-)

[smz]

@Kubik-Rubik Victor, honestly I'd removed those width and height options before merging...

[smz]

... but they do no harm: just ignored.

[Kubik-Rubik]

@smz Since I've merged it already, please do a small PR for it. In #7003 @dgt41 should remove them before merging. Thanks!

[smz]

OK!

[smz]

... or @dgt41 could incorporate that in #7003. I stand-by waiting for @dgt41...

[dgrammatiko]

@smz @Kubik-Rubik will do it in #7003, thanks!