#5 Store last pixel settings and export settings

[Alok Saldanha]

Often people will want to view data with prior pixel settings or
export data with the same settings as before.
To accomodate this, it might be useful for the last pixel settings and
export settings to be saved in a global xml file, and used by default
when a new file is open/exported.
Of course, the values in the JTV file, if present, would override the global
settings.