split ide-config.properties into multiple files

I'd like to split the contents of the current ide-config.properties file into multiple files so the content is easier to maintain via code generation.

So, rather than 1 big file [1] we could split this into 5 files:

• ide-config_4.4.snapshots.properties - contains the properties needed for jbosstools and devstudio CI builds (currently 4.4.2.Final and 10.2.0.GA)
• ide-config_4.4.staging.properties - contains the properties needed for the latest jbosstools and devstudio staging build (currently 4.4.2.AM3 and 10.2.0.AM3)
• ide-config_4.4.development.properties - contains the properties needed for the latest jbosstools and devstudio development build (currently 4.4.2.AM2 and 10.1.0.GA)
• ide-config_4.4.stable.properties - contains the properties needed for the latest jbosstools and devstudio stable build (currently 4.4.1.Final and 10.1.0.GA)
• ide-config.properties - contains all the other properties for 4.3.x and earlier releases

[1] https://github.com/jbosstools/jbosstools-download.jboss.org/blob/master/jbosstools/configuration/ide-config.properties

By splitting this into smaller files, the contents that need to be changed every 3 weeks when we stage or release a build could be generated destructively, rather than having to worry about making changes w/ sed and not accidentally pushing in an invalid URL or value.

From the central side of things, we would just want to treat all ide-config*.properties files as if they were pieces of a single file, and load them all into the same hash of properties we currently have from the single file.