Softserial can now be enabled/disabled via the SOFTSERIAL feature switch in the command line. Softserial baud rate can be set via softserial_baudrate setting. Added input & output inversion support, use softserial_inverted setting by Dominic Clifton

git-svn-id: https://afrodevices.googlecode.com/svn/trunk/baseflight@435 7c89a4a9-59b9-e629-4cfe-3a2d53b20e61