firmware: move ICE LED handling to FPGA code. NFCI. The existence of an FX2 pin dedicated to the ICE LED is an oversight; it should have been hooked up directly to CDONE to save a scarce FX2 pin. Handle the LED transparently in FPGA code, with the aim of eventually freeing its pin on a future revision. Also, eliminate redundant state in the form of ST_FPGA_RDY latched status bit.

device.hardware: fix downloading prebuilt bitstreams. This was broken in commit 7e170bf1.

software: fix broken package_data link. This change was missed in 68f8cfbf, and broke installation through wheels.

firmware, software: introduce revC2 revision code

device.hardware: use hotplug events when waiting for re-enumeration. Before this commit, there was a close race between re-enumeration in the firmware (which takes about a second), and a hardcoded wait in the software (which also took about a second). This would result in spurious errors when firmware needed to be reloaded. After this commit, hotplug events are used when available to remove any hardcoded wait (and make the process a bit faster as well), and on platforms without hotplug events (see libusb/libusb#86), a longer hardcoded wait of 5 seconds is used to make the race less likely to fail.

device.hardware, cli: unbreak `factory --force`. Before this commit, the `factory` command would ignore already factory-programmed devices during enumeration (even if the device was in recovery mode). This defeated the purpose of the `--force` flag. After this commit, the `factory` command would discover any devices, whether factory-programmed or not, such that `--force` works on any device in any state. Closes #236.

applet.debug.arm.jtag: enable debug power. Without debug power, AP enumeration will ~always fail.

applet.debug.arm.jtag: handle AP transactions setting STICKYERR. Also, gracefully handle failures reading AP IDR when enumerating APs.

applet.debug.arm.jtag: new applet. Currently it implements only basic AP enumeration.

arch.arm{→.dap}.{ap,dp}: consolidate. There's *way* too many DAP-related definitions for them not to have their own namespace.