fixes JOO-76
http://jangaroo.myjetbrains.com/youtrack/issue/JOO-76
ExmlcException#getFileName() and #toString() throw NPE for null file

Be robust again null file.
move EXML compiler tests to separate "modules" to allow for cleanly separated sourcepaths
Removed last remains of hidden EXML feature "upper case EXML elements" (see 57f8c491).
- since only one implementation remains, replaced interface ExmlElement by its only implementation
- ExmlModelParser#getConfigClassByName() can no longer be called with a target class name
Create a predictable compile order by sorting the result of File#list(), which does not guarantee any specific order.
This should help against builds succeeding in one environment, but failing on another.
Corrected type in internal method name.
fixes JOO-77
http://jangaroo.myjetbrains.com/youtrack/issue/JOO-77
Imported class not generated in time during EXML compilation

Implemented a new strategy when to generate AS classes from EXML.
ConfigClassRegistry now takes over several of the responsibilities of Exmlc.
Exmlc merely delegates to its ConfigClassRegistry.
Instead of scanning all EXML files using an XML parser, ConfigClassRegistry
now starts with scanning only the file system for all EXML sources, creating
instances of the new helper class ExmlSourceFile. Each ExmlSourceFile instance
keeps track of one to-be-compiled EXML source file, which is first mapped to
a ConfigClass model and later generates an AS config class and
(optionally) and AS target class. All this is done in lazy fashion, and exactly once.
Merge branch 'jangaroo-1'