New features, a little restructuring and better help function in 4.5 - 4.6

I have added the following new extension commands:

* install: install (activates an extension)
* uninstall: uninstall (deactivates extension)
* configure: configure an extension
* fetch: fetch an extension from TER
* import: import an extension from t3x-file

I have done some restructuring of the Tx_Coreapi_Cli_Dispatcher class:
* Extended from t3lib_cli. Supports both (required) arguments and options (such as "--xx=yy")
* Changed dispatching so every command has it's own method (uses reflection to validate parameters).
* Better help function (uses reflection and php doc comments to render the help menu) 

Hope you'll find it usefull!

Best regards

Mads Brunn