allow alphanumeric api levels

Changes several files to Allow API levels to be alphanumberic.
Introduces AndroidAPILevelComparator

Signed-off-by: Gorkem Ercan <gorkem.ercan@gmail.com>
precompile android libs with own target

determines the target level for precompilation of cordova library from
the project.properties file that is shipped with the engine. 

Signed-off-by: Gorkem Ercan <gorkem.ercan@gmail.com>