wagn installation and testing

The main goal of this PR is to be able to test mods in decks. 

Here is the new installation process:
```
wagn new mycoredeck --core-dev	# creates a new deck for testing wagn core 
                                # (asks for path to local wagn installation)
    wagn rspec					# run specs in WAGN_ROOT/spec (alias: rs)
    wagn cucumber				# run cukes in WAGN_ROOT/features (alias: cc)

wagn new mymoddeck --mod-dev	# create a deck prepared for mod testing
    wagn rspec					# run all specs in mods directory
    wagn rspec -m mymod			# run all specs for mymod (supposed to be in mods/mymod/spec)
    wagn rspec -s myset			# run spec myset_spec.rb located somewhere in mods/**/

wagn new mydeck --interactive (-i)      # guides through all installation steps 

wagn seed                      # seed production database (replaces 'rake wagn:create')
wagn seed --test-data          # seed production and test database (replaces 'env RELOAD_TEST_DATA=true rake db:test:prepare')
```
The default configuration for decks is stored in lib/wagn/config and can be overwritten or adapted in the deck's config directory.

the new wagn commands are defined here
(there are so many (minor) changes in this PR, might be helpful to point out some key changes)