Hide dot files and directories (0.1.7 regression)
No longer manually process medium change in cli

Medium change is now handled properly by disk_status/fatfs
FPGA: additional waitstates for uPD7725 core
FPGA: hide BRAM area from software unless unlocked

Some games don't like to see the BRAM area (containing the hook routine
and some state information) or just plain overwrite it in their init
routines. It is now hidden from software unless:

* the IRQ/NMI vectors are read (unlock for 48 CPU cycles)
* an unlock sequence is written to BRAM.
Print card space usage on system information screen
Do not acknowledge IRQ in IRQ/NMI hook

This broke the ocean logo in some cases where the original ISR would
never serve due to overlapping IRQs.
Menu / NMI hook: Unlock BRAM where needed
Add uPD7725 wait-state bitfield in comments
Extract file size string generation to separate function