Added _gradle and _gradlew as symbolic links to gradle.plugin.zsh,
otherwise the plugin was not properly loaded.
Output from `gradlew tasks --all` is now parsed in two levels,
first we find segments between `------...` and a newline.
Second, all those lines are parsed and cleaned using awk
and added to .gradletasknamecache.
Tested on gradle 2.13, and gradlew 2.14.
* Enhanced gradle plugin to parse tasks from a quick execution of the tool
* Added a duplicated function for gradlew completion that uses gradlew internally. Builds like Gradle itself (built with Gradle) are sensitive to being run with a matching gradlew version.
* Fixed broken caching of gradle task names. Added - and -- argument completions.
