Minor fix to mvn build instructions

Change-Id: I20f08473c3c96981f77884b346374d2404964528
Media detail page redone as a "slide-up" panel.

Loads and displays default or English description, and categories.
No caching of this info yet.

Scrollable pane is a ListView, with the title/desc/category label
in a 'header' view along with a spacer view. The height of the spacer
is set dynamically to the height of the total fragment minus 48dp,
giving room for an initially-visible title section and a little
spillover so you can see it's scrollable.

Clicking on a category in the cats list opens the category page in
an external web browser. In the future this should open the category
within the app, but we don't have a per-cat view yet.

Description and category list are not yet editable.

GitHub: https://github.com/wikimedia/apps-android-commons/pull/41
Change-Id: I46d0a77481dbe64a268a72f3efe49ae72168541f