fix h5_dumpmeta
fix bug in XML parser when float values are negative
remove deprecated XML methods (replaced by faster regex versions)
clean up output formatting; remove commented debugging stmnts
start to make Gather.LoadTopography read GPS elevations if no DEM provided
separate picking attributes and methods

picking attributes and methods have now been placed in the PickableGather class,
so that they are cleanly seperated from the CommonMidpointGather and
CommonOffsetGather. This removes cruft from code that doesn't deal with picking,
and makes it simpler to experiment with alternative picking algorithms. This
will temporarily break icepick.py, which now needs to instantiate
PickableCOGather objects.
remove CutRegion and CutSingle methods

these methods have been deprecated for a long while, replaced by the more
flexible and less dangerous CutTraces (and more granular CutMetadata) method.
The only change internal to gather.py was porting FixStaticGPS to use
CutTraces().
bump version nnumber to 0.4
Merge branch 'pickable-gather'
open a PickableCOGather by default in icepick - this is a temporary fix
add object-based command definitions and parser
fixes to command classes and application functions, and started embedding new system into irview
add dynamic filter list to irview 'help'
Merge branch 'filter-classes'
add nicer output to 'ls' command
add dewow as a step in AGC
take cutoff frequency, bandwidth, and nsamples as optional arguments to lowpass/highpass filters
if argument to lowpass_td/highpass_td isn't odd, increment by one
if a command fails, nicely print the error rather than crashing
Added prototype Console and Appwindow classes

in the future, icepick will be based on these classes. For now, they are
very much a work in progress, and their use is not recommended.