Reload OKPay client configuration

Use options on the corresponding SettingsMapping to represent 
unconfigured payment processors and, therefore,  use Option[AccountId] 
in several other interfaces. Also, remove default values from the 
application.conf at coinffeine-gui.

Extract OkPayWebService class from OkPayWebServiceClient. The 
heavyweight initialization is done by the former and we can have
a fresh instance of the latter with the last version of the settings.
Add okpay.ws package

Move there classes related to SOAP access to OKPay
Use current configuration on OkPayProcessorActor

Take a fresh copy of the setting to create a OkPayWebServiceClient, or,
if critical settings are missing use NotConfiguredClient (special case
object for OkPayClient).
Merge pull request #281 from apoloval/fix/currency-textbox

Replace `DecimalNumberTextField` in `OrderSubmissionForm`
Merge pull request #282 from sortega/issue/88_okpay

#88 Fix problems accessing OKPay the first time after the wizard
Make PaymentProcessorActor close its client factory

To do so, change from a lambda of type `() => OkPayClient` to a trait
with two methods: build and shutdown.
Use our own timer and pool executor for dispatch

This allow us to use daemon threads and having a clean shutdown
strategy.
Bump dispatch to 0.11.2

It is the last stable version and this help me to debug the
non-termination problem.
Merge pull request #283 from sortega/issue/73_graceful_exit

Fix Scalaxb preventing a successfull app shutdown
Fix exchange amount and progress shown on the GUI
Notify when exchanges start a handshake
Fix how empty string is handled on CurrencyTextField
Merge pull request #286 from sortega/fixes

Several usability fixes
Make currency amounts conversion to string canonical
Fix BlockchainNotifier logging
Merge pull request #287 from sortega/fixes

Fix how currency amounts are converted to string and BlockchainNotifier logging
Fix representation of 0.BTC as string
Merge pull request #288 from sortega/fixes

Fix representation of 0.BTC as string
Have just one version of netty in the classpath

This fixes the project compilation on IntelliJ
Merge pull request #289 from sortega/make_it_compile

Have just one version of netty in the classpath