Backend: morph exception wrapping at balance chk

This InconsistentResultFromDifferentServersOfSameCurrency
exception type was introduced in [1], but after implementing an
improvement[2] over the exception message and type of another
problem, I realised that the new exception thrown in [2]
wouldn't be covered by the exception type mentioned above, so we
need it to be more generic (to receive any exception as
innerException), so let's do that and rename it.

This commit in conjunction with [2] don't really fix issue
250 [3], but it might mitigate it, and anyway thanks to [1] if
it happens again, we will receive a different exception, with
different exception message as well, so let's close [3].

Closes #250

[1] 8fa47e0
[2] 5eca671
[3] #250

src/GWallet.Backend/Account.fs

@@ -8,9 +8,9 @@ open System.Threading.Tasks
 open GWallet.Backend.FSharpUtil.UwpHacks
 
 // this exception, if it happens, it would cause a crash because we don't handle it yet
-type InconsistentResultFromDifferentServersOfSameCurrency(currency: Currency,
-                                                          innerException: ResultInconsistencyException) =
-    inherit Exception (SPrintF2 "Inconsistent results retrieving info for currency %A: %s"
+type UnhandledCurrencyServerException(currency: Currency,
+                                      innerException: Exception) =
+    inherit Exception (SPrintF2 "Issue when retrieving %A currency balance: %s"
                            currency
                            innerException.Message,
                        innerException)
@@ -55,8 +55,8 @@ module Account =
                                                                                   balance
                         return Fresh compoundBalance
                 with
-                | :? ResultInconsistencyException as innerEx ->
-                    return raise <| InconsistentResultFromDifferentServersOfSameCurrency(account.Currency, innerEx)
+                | ex ->
+                    return raise <| UnhandledCurrencyServerException(account.Currency, ex)
         }
 
     let internal GetAccountFromFile accountFile (currency: Currency) kind: IAccount =