Implement associative arrays for bash services

[Marak]

Right now, bash services are still injecting all request and env parameters into separate unique bash variables ( like how Lua use to work prior to #18 )

It would be better if we used bash 4 feature of associative arrays for creating two objects, Hook.params and Hook.env, which are populated with many items ( instead of creating many unique variable names )

[Marak]

I added the code, but it turns out bash 4 isn't readily installed on many systems.

I'll see if I can get this checked in with dual support for bash 3 and 4.