[DS-2052] @mire Mirage 2 Contribution

[DS-2052] @mire Mirage 2 Contribution
fixed slow build
build with dependencies included now default
Update general.xsl

missed some debugging code
added support for multiple mirage 2 versions
added support for multiple mirage 2 versions - for deps included mode
cleanup after multiple mirage 2 versions addition
fixed an issue where the thumbnail placeholder wouldn't be shown in discovery results
name change
Added sections on customisation and using multiple themes
Fixed a typo
move mirage2 messages and dynamically fill theme name in sitemap
Merge branch 'mirage2-contribution' of https://github.com/atmire/DSpace into mirage2-contribution
DS-2077 Sort collections by full path

This commit fixes the order of collection drop-down entries when starting a
submission and when editing e-mail subscriptions such that the community
hierarchy is taken into account as well as the collection name. The change in
CollectionDropDown makes the same mechanism re-usable in other places where
this might be required.
Added missing filtering for the dependencies included install.
Removed accidentally committed mirage2 as default xmlui.xconf
Removed references to removed Mirage2 aspect.
DS-2088 Record bitstream downloads as Google Analytics events
Merge pull request #587 from atmire/mirage2-contribution

[DS-2052] @mire Mirage 2 Contribution
Merge pull request #610 from robintaylor/DS-2088

DS-2088 Record bitstream downloads as Google Analytics events
Merge pull request #586 from aschweer/DS-2077-sort-collection-dropdown

Ds 2077 sort collection dropdown
Travis tweaks. Speed things up by skipping 'install'. Give Maven more
memory.