Multiple fixes

* Implemented ScriptRunner with environment expansion and cleaner
  code.
* Added ApiClient plugin (com.noccy.apiclient)
* Renamed CHANGELOG.md to VERSIONS.md
* Shuffled buildtools
* Added first unittests

README.md

@@ -81,7 +81,7 @@ The advantage of writing your extensions as plugins:
 Using scripts is the simplest way to leverage Spark:
 
 *spark.json*
-```
+```json
 {
   ...
   "scripts": {
@@ -95,14 +95,16 @@ Using scripts is the simplest way to leverage Spark:
 }
 ```
 
-`.php`-files are executed in-process, and as such have access to any registered
-resources, resource types and plugins.
-
-*Note: The script system need to be improved and revamped to support environment variables and such*
+- Call on other scripts by prepending `@` to the script name.
+- `.php`-files are executed in-process, and as such have access to any registered
+  resources, resource types and plugins.
+- `.phar` files are still executed out-of-process, as are any commands that don't
+  match a PHP callable or any other specific rule.
+- Substitute shell variables using `${varname}`.
 
 ### Resources
 
 Resources are wrappers around database connections and such, providing a cleaner
 interface to its innards.
 
-Resources are generally registered by plugins.
+Resources are generally registered by plugins or local scripts.