Support optional --cache-dir program parameter and cacheDir manifest entry

[edvin]

The cache dir option will override the directory the downloaded artifacts are placed in. By default, artifacts are placed in the current working directory. The program parameter --cache-dir or the manifest entry cacheDir can be specified to override this.

If the cache dir parameter starts with the magical string USERLIB/ this string will be replaced with an OS specific path. Consider the following parameter value:

fxlauncher.jar --cache-dir=USERLIB/MyApp

The result will be:

OS	Location
Windows	~/AppData/MyApp
Mac	~/Library/Application Support/MyApp
Linux	~/.MyApp

This feature can be helpful in several circumstances:

• If the application is installed in a placed where the user does not have write access
• If there is a problem with configuring the current working directory, as seen with some Mac Java Version
• To cache commonly used library files amongst several installed apps

The program parameter will override any configured value in the manifest, and the default will still be "the current working directory".

[edvin]

Implemented in 1.0.10