Clean copies of GridMath and FieldImpl

from latest IDV/VisAD 2014-05-14

[1720]
Initial proof of concept: keep metadata in FI

- FieldImpl.java:  add metadata HashMap field

- background.py: scripting hooks to utilize new metadata field
    - Get rid of binary overrides... doing e.g. "sub(a,b)" will now just
      return a plain FlatField, but layer labels will still work due to
      retained metadata.  So the binary overrides should be unnecessary.
    - createLayer gets layer labels from new FieldImpl metadata,
      not _MappedData dictionary
    - _MappedData constructor initializes FieldImpl metadata

- GridMath.java: demo of keeping track of metadata in "subtract"

[1720]
Set working directory to value of "mcv.userpath".

[1327]
Local override of GridUtil. [1327]

There is being done to satisfy the default path stuff from Inquiry
1327. I may also fix the deprecation warnings prior to submitting a
pull request.
Fix default path bug. [1327]

This modifies “exportGridToNetcdf” and “writeGridToXls” to use the
“user.dir”/“mcv.userpath” System property (if the user has not
specified the exact path).
Add option to User Preferences that displays a logo by default [1212]
Merge remote-tracking branch 'upstream/master' into metadata
Implement Jon's suggestions

- Move metadataMap initialization into constructor
- use ConcurrentHashMap
- fix metadataMap setter (nice catch Jon!)

[1720]
Merge pull request #90 from mhiley/metadata

Initial proof of concept: keep metadata in FieldImpl
Set initial size of Offset box to accommodate all valid entries [1212]
Remove explicit set of user.dir to mcv.userpath [1327]
Give logo position a default value at system startup [1212]
Handle presence of ellipsoid and terrain-corrected geo in same file for DNB [1738]
Temporary product fields for terrain corrected Height, Lat, Lon [1738]
[0] Dreamweaver updates synced from web server.
Add keyword args to transform_flatfields. [1338]
Add transform_flatfields to cleanFilter. [1338]

There was also a second (apparently identical except for whitespace)
cleanFilter function that I’ve removed.
Remove local override of AreaImageFlatField

It shouldn't be necessary now since we aren't overriding "binary"

[1720]
ConcurrentHashMap doesn't allow null values [1720]
[0] Dreamweaver updates synced from web server.