Add support for Indicate

[vincentbrison]

Thanks for the awesome work.

Currently the lib only support notification through Notify (check setCharacteristicNotificationsEnabledOnRemoteDevice).

There is a second way of doing notification through Indicate.

From Android perspective it mostly works exactly as notification. Adding support for Indicate in the library would only require minor changes. It could be done using same code as setCharacteristicNotificationsEnabledOnRemoteDevice but using Indicate fields counter part (BGD.ENABLE_INDICATION_VALUE and BGC.PROPERTY_INDICATE). It would also require doing the same work for openNotificationSubscription

Would you accept contribution on this subject?
Thanks, have a good day

[LouisCAD]

Hello, sorry for the long time without news.
If you're still up for it, feel free to send a PR starting with a setCharacteristicIndicationsEnabledOnRemoteDevice function.

As for the openNotificationSubscription function, it's been deprecated in v0.5.0 in favor of notifications, so I'd think about a function named indications`.