WIP: move to a more configurable approach

* mkt is now a command installed at setup
* the fig.yml.dist, images and base-images are all in the python package
* the trees all exist in one place, so still configurable as a file share
* the trees can be used if they already exist, no need to change anything

Example:
```
$ pip install marketplace-docker
$ mkt root ~/sandboxes/
Set the following environment variable: 
FIG_FILE=/Users/andy/.mkt.fig.yml

Saving root to /Users/andy/.wharfie
Written fig file to /Users/andy/.mkt.fig.yml
$ export FIG_FILE=/Users/andy/.mkt.fig.yml
$ fig up spartacus
Recreating andy_spartacus_1...
Attaching to andy_spartacus_1
```
Looking for general feedback, there's cleaning and so on to do here. 

The thing I like is that things like checkout still work, the fig file is now templated, existing devs can setup docker really quickly because they point at their existing checkout and `mkt` and `fig` are now global without having to mess around inside wharfie.