Pairformatter for Kraken needs DASH Edge Case Handling

[deepbrook]

With DASH now supported by Kraken, the currently implemented formatter needs a special case handler for this pair, since the currency does not use the prefix X, like other pairs (i.e. DASHEUR is denoted as DASHZEUR instead of XDASHZEUR, which would have been the expected behaviour).

Excerpt from /AssetPairs endpoint:

{ [...]"result": 
{"DASHEUR":{
    "altname":"DASHEUR",
    "aclass_base":"currency",
    "base":"DASH",  # <-- expected format would have been XDASH, as is true for other pairs
    "aclass_quote":"currency",
    "quote":"ZEUR", [...]},
[...]}```