Support exclusions and credentials, and 2 minor fix

First of all, thanks for your great work :)

Currently, I'm working on java maven project but I need some dynamic shell like `sbt console`.
So, I just stared applying this plugin and find some minor problems like below.

### Features
- exclusions
- credentials

### Defects
- property name can't have "-" char
- scope sometimes go wrong with its version

This request contains the changes for above features and defects.


Thanks again !