Update database_schema.rst

dbsnp updated to version 137
--sample-filter added.

This allows for SQL-style queries on the sample table and
deprecates the --phenotype and --exclude-phenotype type
functionality.
Merge branch 'master' of github.com:arq5x/gemini
Switched family-query test to use the --min-kindreds option.

Also fixed a bug with a missing tab in the expected output to
cause the unit test to fail.
Merge pull request #203 from tanglingfung/patch-3

Update database_schema.rst, thanks to @tanglingfung
Extended PED format added.

The PED file loaded with GEMINI can now have arbitrary columns after the
requisite 6, if a header starting with # is added. The columns in the GEMINI
database will be the names in the header.

For example:
\#family_id sample_id paternal_id maternal_id sex phenotype ethnicity hair_color
1 M10475    None None  1    1    None   brown
1 M10478     M10475  M10500    2    2    None   brown
1 M10500     None    None    2    2    None purple
1 M128215    M10475  M10500    1    1    None blue
Merge branch 'master' of github.com:arq5x/gemini
Clean up some unused options for gemini query.
Fixed variant_samples etc all showing up when not requested.
Clarity edits, some docstrings added.

Removed unused partition function.
[ENH] auto_* tools work without parents
[DOC] update auto_* tools re: parents no longer required.
tweaks to auto_rec functionality for unaffected children
resolve conflicts
add missing test files
fix merge goof
Add a --devel flag to update allowing explicit retrieval of latest GitHub version