Add at-commander library as a submodule.
Draft addition of baud rate initialization for PIC32 builds.
Add a draft of setting UART accessory baud rate for LPC17xx boards.
Don't enable receive line status interrupt for UART, we don't care.
Remove duplicate GPIO set.
Add debugging when setting baud rate on LPC17xx.
Re-organize UART init for LPC17xx to allow changing baud on the fly.
Update atcommander library to fix bugs.
Fix UART baud rate.
Remove extra log message.
Don't pre-init UART before setting baud rate.
Temp. enable auto-rts when setting baud rate.

What's insufficient with our manual setup?
Re-add a slight delay to allow RN-4x to boot up before setting baud.
Merge branch 'next' into atcommander
Make sure UART rx is active on bootup.
Reset RTS state to inactive when re-initializing UART.

This fixes the issues with flow our manual flow control implementation
described in #91.
Move baud rate to inside the UartDevice struct.
Wait after rebooting RN-42 to avoid locking it in an off state.

This may fix #135.
Match delay function with common type signature.
Move RN-4x initialization to a generic bluetooth namespace.