Add mustExist attribute to file fields.
Do not print 'null' during console installation if no label is defined
for a file field. This could easily come up when the user decides to use
    a description tag for their file field instead.
Updated xsd.
[IZPACK-1137] Variables not resolved in default values and labels of user input fields
Merge pull request #239 from izpack/IZPACK-1137

[IZPACK-1137] Variables not resolved in default values and labels of user input fields
[IZPACK-1090] Allow tab completion and password masking in console mode
- Falling back to read lines from standard input instead of failing the installation if ConsoleReader initialization fails ClassNotFoundException (occurs when the JNI DLL loading/initialization fails) (TODO: stabilize initialization on Windows)
- Suppress JLine logging completely for now (TODO: connect it to IzPack logging)
- Small cleanups
Merge pull request #240 from rkrell/IZPACK-1090

[IZPACK-1090] Allow tab completion and password masking in console mode
[IZPACK-1090] Allow tab completion and password masking in console mode
Post-fix: Really suppress logging from the beginning (there are cases
when the ConsoleReader doesn't throw any error but still doesn't work.
Merge pull request #241 from rkrell/IZPACK-1090

[IZPACK-1090] Allow tab completion and password masking in console mode
[IZPACK-1090] Allow tab completion and password masking in console mode
Post-fixes:
- Really recognize fallback if ConsoleReader cannot be initialized.
On Windows, in some cases it didn't throw an error but initialized an UnsupportedTerminal which made the password field masking not working
- Use System.console() from JDK 1.6 instead of accessing System.in and System.out. Old style left als fallback for unit tests, which can't read System.console().
Merge pull request #242 from rkrell/IZPACK-1090

[IZPACK-1090] Allow tab completion and password masking in console mode
Ensure header is not shifted by 12 pixels
Ignore agentpath argument to jvm
Merge pull request #244 from ahmedlawi92/IZPACK-1139

IZPACK-1139 - Ignore agentpath argument to jvm
Merge pull request #243 from mtjandra/IZPACK-1140

[IZPACK-1140] - Ensure header is not shifted by 12 pixels
Fix for IZPACK-1009; update javadocs to have fewer missing piece of information.
RulesEngineImpl changed so that operands are not blindly added to the list of
operands for AndCondition / OrCondition / XorCondition. Instead, each condition
(and sub-condition) is checked for existence before being added; if any operand
in any expression doesn't exist, the whole expression will evaluate to false.
fix the complex expressions also
IZPACK-1109: align the warning messages to use the same language
- Ensure splash screen is only shown for GUI installations
- SplashScreen should only be shown if user has specified to use one in
  the guiprefs of their install.xml.
- New useSplashScreen modifier allows the user to specified minimum
  amount of time to display splash screen
- Notice that the splash screen must be displayed outside of the
  runnable, otherwise the splash screen will be grey
- Remove logic for adding splash screen to the Manifest