Fix setting of android sdk tags file.

Using &tags variable to add the android sdk tags file was not working for some
reason. I ended with an error indicating no tags file error.

Now we use execute to set the tags file and it seems to be working ok.
Implement methods to update ctag files.

New methods to create ctag files that can be used for fast source code
navigation, auto-completion and tagbar.
Create gitignore file.
Fallback android#install() method if no device found.

If no android devices or emulators are found when calling android#install()
fallback to android#compile().

Also improve the compilation process output by adding log messages indicating
what device was installed.