improve: GpCommandLineParser: allow to restrict for assign published properties only

[ashumkin]

Sometimes a target class can have a public property of a custom
enumeration type which is set from a string value from a command line.
E.g.
type
TLogLevel = (llTrace, llDebug, ...

TCommandLine = class
private
  FLogLevel: TLogLevel
public
  property LogLevel: TLogLevel read FLogLevel write FLogLevel;

  [CLPLongName('log-level')]
  property LogLevelAsStr: string read GetLogLevelAsStr write SetLogLevelAsStr;
end;

In this case TGpCommandLineParser raises the SUnsupportedPropertyType
exception for LogLevel property as it supports Integer, String and
Boolean types only.

Let's fix it by adding opPublishedPropertiesOnly option to tell a parser
to respect published properties only.
So, TCommandLine will appear to be defined as the following

TCommandLine = class
private
  FLogLevel: TLogLevel
public
  property LogLevel: TLogLevel read FLogLevel write FLogLevel;
published
  [CLPLongName('log-level')]
  property LogLevelAsStr: string read GetLogLevelAsStr write SetLogLevelAsStr;
end;