Aliases for bus naming

[gbowers4]

Bus naming is very strict - users may have an in-house standard for bus suffixes - an optional alias arg has been useful for changing this

_signals = ["valid", "data", "startofpacket", "endofpacket"]

the above is the standard - we have been using something similar to:

_aliases = {
    "startofpacket": "sop",
    "endofpacket": "eop"
}

def __init__(self, entity, name, clock, config={}, **kwargs):
    AVSTDriver.__init__(self, entity, name, clock, config=config, aliases=self._aliases, **kwargs)