add watch face to display files on the filesystem

[joeycastillo]

Simple watch face, displays numbered files FILE0000.TXT, FILE0001.TXT until looping around when a file is not found. When used in conjunction with the irda_upload_face, this should function as a databank that you can update without cracking open the watch.

File format is plain ASCII text and must be exactly 12 characters long:

• the first three characters appear in the top left position on the custom LCD. if using the classic LCD, the third character is ignored.
• the next two characters appear in the top right
• the six characters after that appear in the bottom
• one final character sets the indicators. if no indicators are needed, use a space ( )

The last character acts as a bitmask for setting indicators. Bit 5 is always set, and does not correspond to any indicator.

• Bit 0 (0b00100001 / !) sets the bell indicator
• Bit 1 (0b00100010 / ") sets the PM indicator
• Bit 2 (0b00100100 / $) sets the colon
• Bit 3 (0b00101000 / () sets the LAP indicator
• Bit 4 (0b00110000 / 0) sets the decimal point on the custom LCD
• Bit 6 (0b01100000 / `) sets the leading 1 on the custom LCD

You can mix and match these, so to set both the colon and the PM indicator, you'd use the ampersand & (0b00100110)