Change SimpleSAMLphp config folder on demand

[antons-]

Couple of issues here:

• As SilverStripe environments dev|test|live are typically run on different servers, each environment potentially requires a different SimpleSAMLphp config.
• SimpleSAMLphp upgrades via composer will delete everything in the module, including the config unless the developer backs them up manually before update, or creates a composer script to automate this.
• CWP doesn't allow SSH access to its servers, and only allows files to be pulled in via composer. If we can change the SimpleSAMLphp config location from within SilverStripe, we don't need to resort to heavily modifying the SimpleSAMLphp library.

This will most likely require the creation of a SimpleSAMLphp module that can receive the config path location from a SilverStripe CLI call.

A working implementation has been achieved on the CWP fork, this needs to be tidied up and pulled in here as this isn't CWP specific