This commit adds support for at least some of the Serial boards with the
CH341 chipset, tested using a board from sparkfun as well as one from
Amazon.com

The code was rearranged some of the Claim code and added a VID:DID to Serial Type table that I use to map, such that I know some of these devices have multiple valid setups.

Support Begin/End/Begin - Change baud

Added code to support switching baud rates, or more particular be able to call end() and then call begin(...) with same or different baud rate.

Hopefully some support for also releasing DTR when the end is called.

WIP - Start support for the begin(baud, format)

Adding some support to the code to handle some of the different possible format capabilities.

In particualar trying to handle the parity, number of bits and number of stop bits.

hacked up test app, such that if you type in command line like:
"#9600, 7e1"

It will extract the 9600 as the new baud and try to use format 7e1.  I only hard coded a few of these in the test app (8n1, 7e1, 7e2, 8n2)...

Again work in progress.  Took me awhile tofigure out how to do this for ch341 boards as I did not see any documents or code that handled this.  So had to deduce it from differences in USB packets.

This commit should start to allow some Prolific PL2303 devices to work.
Tis device has a rather more complex initialization process than some
of the other devices.

I have tested this some with one device that I used to use to program
some older RS232 based boards plus talk to an SSC-32 device.
Test case is I am able to talk to SSC-32 and if I type in ver<cr>
It does properly return the version number.

The data I am seeing is pretty close to what
was documented in: https://gist.github.com/tommie/89011c5ac06553d5cdb8
as well as what the Linux driver outputs.

I also incorperated Frank's configuration options.

Have some support in place for the CDCACM serial class code.

It appears to be working for talking to a
Teensy that is programmed USB=Serial
or USB=Serial+...

Also test with an USB2AX board which is a Servo controller for Dynamixel servos (AX-12), that is an Atmega32u2 board programmed using LUFA as the USB library.