Improved built-in help

I changed how the built-in help works (got tired of seeing so much information every time). Now it look at what the user attempted to type. 
Example:

    RFIDler> w
        WIEGAND-LEARN                                                Learn Wiegand input timings
        WIEGAND-OUT <OFF|ON>                                         Set Wiegand output OFF or ON
        WIEGAND-READ                                                 Read Wiegand input
        WIEGAND-WRITE <BINARY>                                       Send Wiegand output
        WIPE                                                         Wipe NVM
        WRITE <BLOCK> <HEX DATA>                                     Write data block (may require login/auth)
        WIRING                                                       Show wiring diagram (alias: WIRES PINS)
    Note: '*' prepended to main prompt indicates unsaved config changes

    RFIDler> wie
        WIEGAND-LEARN                                                Learn Wiegand input timings
        WIEGAND-OUT <OFF|ON>                                         Set Wiegand output OFF or ON
        WIEGAND-READ                                                 Read Wiegand input
        WIEGAND-WRITE <BINARY>                                       Send Wiegand output
    Note: '*' prepended to main prompt indicates unsaved config changes

    RFIDler> help as
        ASK <HEX UID> <FC> <RATE> <REPEAT>                           Emulate ASK, Field Clock in uS/100, Data Rate in RF/n
    Note: '*' prepended to main prompt indicates unsaved config changes

    RFIDler> help wipe
        WIPE                                                         Wipe NVM
    Note: '*' prepended to main prompt indicates unsaved config changes

As before, you can type "" or "HELP" to see all the help info. 

The commits before were some docs on setting up build-environ on linux.