Implementing LauncherOption enum and supporting classes

[IainDavis]

Problem Statement

Current implementation of configurable options is ad-hoc and based on Strings.

Proposed fix

Centralize and standardize the set of configurable options for the Launcher program in an enumerated type with responibility for:

• giving each option an constant Java symbol that represents it
• defining the String that will be used to associate a given command-line entry or member of a Java properties file with the option
• supplying default values for each option
• providing validation logic for each option
• providing a Resolver mechanism for any needed transformation of an option (i.e., as with the ALLUSERS and USERLIB path sections in CACHE_DIR).
• tracking when in the FxLauncher's lifecycle a particular property was set

Steps taken

1. Introduced several new packages to organize functionality
2. Introduced the described enum class
3. Introduced supporting enums GenericPathLabel and OS that together have responsibility for resolving the ALLUSERS and USERLIB sentinels
4. Introduced a Resolver interface, which extends UnaryOperator<String> along with some default implementations
5. Introduced a Validator interface which extends Predicate<String> along with some default implementations

Additional steps taken that are not necessarily relevant to the current work but will affect later-planned work.

1. Added enum LifecyclePhase that acts as a very simple state machine and implements an Observable pattern
2. Added a LifecycleListener interface that Observers of LifecyclePhase must implement
3. Added application-specific Exception types