Unify search code

Right now we have two features, commerce_kickstart_search and commerce_kickstart_lite_search.
Each one has an index for the matching install "flavor" (demo store or no demo store).
Each one also has the exact same set of custom plugins.
The product_ui features duplicate the actual view, the current_search settings, theme tweaks.

Not counting the plugins, removing the duplication would allow us to remove about 400 lines of code, while also killing many
bugs (sometimes fixes were only applied to one version of the code).

Plan:
1) Move the server creation to commerce_kickstart_install(). Instead of a huge export, we solve it in 10 lines of code.
2) Since the indexes depend on the actual fields attached to the product types (at least until we write some code that creates indexes automatically instead of using an export), place them on the product features.
3) All other code (plugins, view, current_search, theme tweaks) goes into commerce_kickstart_search which is enabled for both install flavours.