Remove obsolete status-related classes

We use the SciJava Context's StatusService now.
AxisGuesser: use private, not protected, fields

Protected fields ruin extensibility; see:
http://developer.imagej.net/coding-style#Private_over_protected_fields_and_methods
SCIFIO: leverage SJC 1.7.0's richer Gateway

We now inherit service shortcuts for the SciJava Common level,
as well as some handy AppService shortcuts.