clearPsk

A simple pre-shared key for now for crypto.
Must be either 0 bytes (no crypto), 16 bytes (AES128), or 32 bytes (AES256).
A special shorthand is used for 1 byte long psks.
These psks should be treated as only minimally secure,
because they are listed in this source code.
Those bytes are mapped using the following scheme:
`0` = No crypto
`1` = The special "default" channel key: {0xd4, 0xf1, 0xbb, 0x3a, 0x20, 0x29, 0x07, 0x59, 0xf0, 0xbc, 0xff, 0xab, 0xcf, 0x4e, 0x69, 0x01}
`2` through 10 = The default channel key, except with 1 through 9 added to the last byte.
Shown to user as simple1 through 10