Report only hardware capabilities that we actually have

We're currently reporting a bunch of hardware capabilities (camera,
microphone, compass, GPS) which we don't actually have.  Presumably this
was done because these capabilities were required by the compatibility
definition once upon a time and apps implicitly depended on their
presence, but with the revision of the CDD to accommodate basic
wifi-only tablets and the proliferation of such devices on the market,
this should no longer be necessary.
Remove unused recovery.fstab

The recovery now uses the unified fstab.encore, so this file is
obsolete and unused.  Remove it.
Clean up BoardConfig.mk

encore's been around an unusually long time, and in that time it's
picked up quite a lot of cruft in BoardConfig.mk; it's time for a
housecleaning.  Specifically:

* Remove flags for which no other references exist in the CM source tree
* Reorganize remaining configuration into some semblance of a logical
  grouping and order
Remove optimization settings from BoardConfig.mk

It's no longer possible to override the optimization settings chosen by
the build system this way, so these settings currently have no effect at
all.
Move device-installed scripts under prebuilt/

This provides clear separation between shell scripts which are intended for
the build host and those which are intended for the device.