Kernel minimization (#334)

* adds patch to remove unused kernel components

* new boards, rebase patches to match

* rename boards for deployment

boards/nordic/nrf52840dk_opensk/README.md

@@ -0,0 +1,65 @@
+Platform-Specific Instructions: nRF52840-DK
+===================================
+
+This is an adapted nrf52840dk made to work with OpenSK.
+
+The [nRF52840 Development
+Kit](https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF52840-DK) is a platform
+based around the nRF52840, an SoC with an ARM Cortex-M4 and a BLE
+radio. The kit is Arduino shield compatible and includes several
+buttons.
+
+## Getting Started
+
+First, follow the [Tock Getting Started guide](../../../doc/Getting_Started.md)
+
+JTAG is the preferred method to program. The development kit has an
+integrated JTAG debugger, you simply need to [install JTAG
+software](../../../doc/Getting_Started.md#loading-the-kernel-onto-a-board).
+
+## Programming the kernel
+Once you have all software installed, you should be able to simply run
+make flash in this directory to install a fresh kernel.
+
+## Programming user-level applications
+You can program an application over USB using the integrated JTAG and `tockloader`:
+
+```bash
+$ cd libtock-c/examples/<app>
+$ make
+$ tockloader install --jlink --board nrf52dk
+```
+
+The same options (`--jlink --board nrf52dk`) must be passed for other tockloader commands
+such as `erase-apps` or `list`.
+
+Viewing console output on the nrf52840dk is slightly different from other boards. You must use
+```bash
+$ tockloader listen
+```
+**followed by a press of the reset button** in order to view console output starting from the boot
+sequence. Notably, you should not
+pass the `--jlink` option to `tockloader listen`.
+
+## Console output
+
+This board supports two methods for writing messages to a console interface
+(console driver for applications as well as debug statements in the kernel).
+
+By default, messages are written to a UART interface over the GPIO pins `P0.05`
+to `P0.08` (see the [main.rs](src/main.rs) file).
+
+If you don't have any UART cables or want to use a different interface, there is
+also a console over the Segger RTT protocol. This only requires a micro-USB
+cable on the USB debugging port (the same used to flash Tock on the board), and
+is enabled by setting the `USB_DEBUGGING` constant to `true` in the
+[main.rs](src/main.rs) file.
+This disables the UART interface.
+
+For instructions about how to receive RTT messages on the host, see the
+[corresponding capsule](../../../capsules/src/segger_rtt.rs).
+
+## Debugging
+
+See the [nrf52dk README](../nrf52dk/README.md) for information about debugging
+the nRF52840dk.