Updates to the woopra android SDK to make it work better with android

Changes include

- Lots of code improvements
- a more detailed user agent with lots of data about the device
- support for multiple trackers
- fixing thread safety bugs
- bug fix: timeout is now ms vs seconds
- vistor is now uses the same cookie for each device
- adding values for browser, screen size, app, and langage
- changed package name to reflect that it is an android tracker
- included licence (apache 2.0)
- made SDK an android library