Change RunnerCatalog.selection_id type to int

[petedmarsh]

Previously RunnerCatalog.selection_id was declared to be a float, however the API documentation says that it is a long:

https://api.developer.betfair.com/services/webapps/docs/x/SIA6#BettingTypeDefinitions-RunnerCatalog

This changes the declared data type in the model to int. int is used over long as this maintains Python 3 compatability (in Python 2 int('') will return a long if the number is big enough to require it)

(apologies, I should have done this with my PR for Runner.selection_id)

[petedmarsh]

ClearedOrderSummary too!

[petedmarsh]

And some others!

[jmcarp]

Thanks!