Various changes

- Change URL in order to align with iOS SDK : timestamp is used with
_d=1
- Fix issue with URL encoding of parameters (if the property value
contains a & for example)
- Utils to format URL, and usage of StringBuilder to optimise the code
- Ability to set a Bundle of property at initialisation
- In airplane mode the data were removed. Fixed that by checking
network availability before trying to send
- Add a Broadcastreceiver in order to send the data when the network is
back (need to be registered in the manifest)
- Use Android Bundle instead of HashMap<String, String> - deprecated
methods
- Logs only in Debug