[r2dbe_adc_lib] Fleshed out the onepps block a bit.

I added an internal 1PPS generator which is armed to the external
GPS 1PPS. Also, added simple statistic counters that measure the
number of external Maser and GPS pulses received and the period of
the last pulse. This was all stolen from the sma_corr sync block.
[r2dbe_top] Moved the quantize block to the ADC sub-library.
[r2dbe_adc_lib] The quantize block now interprets data as signed with binary point.

Before it would interpret its input data as unsigned 8-bits with no binary point,
then multiply by the gain factor which was unsigned 16-bits with a 12-bit binary
point, until finally re-interpreting the output as unsigned 2-bit no binary point.
This was non-ideal and resulted in incorrect 2-bit statistics.

This commit changes this scheme to use signed and N-1 binary point data for both
the 8-bit input and the 2-bit output, while changing the programmable gain to an
unsigned 16-bit, 8-bit binary point value, allowing for a range of gains of
1/256 <= gain < 256.
[r2dbe_top] The vdif_0 block had changes wrt. to library. Undid this.
[r2dbe_top] Fleshed out the noise_gen block with WGN (copied from SWARM).

Also, moved the block into the ADC sub-library.
[r2dbe_top] Removed the trailing "_0" from quantize block in ADC sub-library.

Also updated the reference to it in the top level diagram.
[r2dbe_adc_lib/noise_gen] Fixed incorrect library links to software registers.
[casper_files/quant.m] This function is needed in the WGN generator.