BluetoothLeGatt Sample

[danardelean]

Fixes:

-Converted to JavaList and JavaDictionary to work with the ExpandableList -Use SetAdapter instead of Adapter property -Filter the already added devices OnLeScan using bluetooth address and not the object itself to avoid adding the same device more than once -Modified the method Lookup in SampleGattAttributes that was crashing the application

Improvments: -When manually disconnecting from a device I am also closing the connection (trying to reuse the connection on some devices will take almost one minute to have the connection established again)

[conceptdev]

Thanks for submitting, we'll review shortly

[gabornemeth]

If this is going to be merged, my pull request has to be canceled, as it fixes the same errors but not all of them. https://github.com/xamarin/monodroid-samples/pull/73