Add EMPTY tile state instead of using null for empty tiles
Add new tracking and tracking_options property
Add jquery 1.7.2 and adapt examples externs

Add jquery and update the externs for the examples (code from @bartvde).
The lib is saved into the repository to be able to run the examples
and the check-examples target offline.
Clean up fixme target

Correct regular expression
Use single quotes consistently
Use format strings
Correct grammar
Merge pull request #343 from twpayne/clean-up-fixme-target

Clean up fixme target
Add semi-transparent layer example
Merge pull request #306 from fredj/geolocation

Activate / deactivate geolocation
Merge pull request #341 from fredj/jquery-examples

Add jquery 1.7.2 and adapt examples externs
Merge pull request #344 from twpayne/semi-transparent-example

Add semi-transparent layer example
Merge pull request #324 from twpayne/fix-canvas-renderer-clear

Canvas renderer is not properly cleared