Issue #1179: Move the construction of the javac arguments to the @PostConstruct method, so any IllegalArgumentExceptions are rethrow as OptionArgumentExceptions and reported nicely by CeylonTool. Use the relevant JavacOption to validate the module specs which we will pass to javac as its file arguments, so we reject things (such as '3') which are neither source file names nor module names.
Issue #1179: Add a test.
ceylon compile: Validation of --javac option arguments (further to #1179)
test: Validation of --javac, end --encoding options and <module-or-source-file> arguments (further to #1179)
Validation of --encoding option arguments and detect non-existent modules
(when the module name doesn't end with .ceylon or .java) (further to #1179)
Fix error in ceylon compile doc.