The documentation covers topics not specifically relevant to libmaple,
so it doesn't make sense for it to be part of the libmaple source
distribution.
Delete the docs/ tree, and prepare libmaple for use with the new
leaflabs-docs repo, which will contain the docs from now on.
* README: update to reflect this change
* support/doxygen/Doxyfile: This is the old docs/Doxyfile
* Makefile: Add a doxygen target
* wirish/comm/HardwareSerial.h: fix reference to docs/. The comment
informing maintainers that the HardwareSerial interface is
documented by hand refers to the docs/ tree, which no longer exists.
Update it to refer to the separate leaflabs-docs repository.
* support/scripts/copy-to-ide: No longer build the documentation
