[conf] remove obsolete USE_SYS_TIME

was only needed for old stm3 vector table, is now already long obsolete and used nowhere
[airborne] cleanup USE_USB_SERIAL
[tools] fix gen_modules_doc.py

properly check if module xml could be parsed
[modules] fix malformed xml files
[conf] remove outdated/unused firmware xml files
[usb_telemetry] Fixed fetching device serial number
[stm32] add usb_tunnel, cleanup setup makefile

also replace usb_tunnel_0 and usb_tunnel_1 on lpc with one usb_tunnel target with configurable uart
[stm32] usb_serial: check if connected in putchar and send

cleanup and rename VCOM_transmit_message to VCOM_send_message
[setup] one usb_tunnel for both lpc21 and stm32
[led] add LED_AVAILABLE macro
[modules] dox for nav_survey_poly_osam
[rotorcraft] allow to turn off motors in failsafe mode

Allow arming/disarming motor as long as not in KILL mode and ahrs is aligned.
[modules] start pimping dependencies

Start working on #940

This replaces
```xml
<depend require="foo|bar" conflict="baz"/>
```
with
```xml
<depends>foo,bar</depends>
<conflicts>baz</conflicts>
```

and now allows to specify OR dependencies with | (pipe) similaro to Debian depends:
```xml
<depends>foo,bar,this|that</depends>
```
which would depend on: foo AND bar AND (this OR that)