Tagged untagged blocks for software.

Please tag new blocks! casper:<block_name> or xps:<block_name>
setting the default board to ROACH2

Also adding the TGE yellow block option for promiscous mode
adding promisc mode to the kat tge core for R2

Setting the promisc mode allows all traffic through to the fabric
except packets destined for the cpu port, use this option if
broadcast traffic is crashing the PPC. It allows the fabric to
see all packets that arrive on the interface.
Missed this, new casper tags for blocks.
Fixed incorrect exception handling.

Also made provision for newlines on values from blocks.
Input port data width bug

One input port was not being configured to have 72 bits when on
ROACH2.
Merge branch 'master' of github.com:ska-sa/mlib_devel
XSG block included in design info,
Merge branch 'master' of github.com:ska-sa/mlib_devel
Revert "Revert "sysclk_2x calculation fix - integer rounding error""

This reverts commit e7d562295857e415a337eb7b6f3613ffb385817b.
Use pipeline blocks instead of regular delays...

...inside bitsnap blocks, before the snapshot.
Merge branch 'master' of github.com:ska-sa/mlib_devel
Bug in SPEAD packetiser fixed.
SPEAD packer updated for correct packet length.
SPEAD pack/unpack direct address missing bit fix
Can't rename a block then access it.
SPEAD header string processing and masks updated
Helper scripts on the right-click menu.
SPEAD ctr and const bits widths fixed.
Corrected malformed case statement for MKDIG