Bug 1873121: HTML / PDF export of Gallery block in slideshow mode is broken

- added carouselHeight() in to viewcontent.tpl to fix display for export preview modal
- added carouselHeight() to export view.tpl to fix display for html export
- added in script tags to export header.tpl to include neccessary funcs
- added code changes to raw, custom theme.js
- added window level scope to carouselHeight ()

Change-Id: I93c44b1b356434eac2d4b8a062166528eaa07999
Signed-off-by: Lisa Seeto <lisaseeto@catalyst.net.nz>
(cherry picked from commit 5e5cf6c1)