docs - foreign data wrapper sql and catalog ref page updates

[lisakowen]

in this PR:

• update FDW-related sql and catalog ref pages to postgresql 9.4
• add greenplum-specific foreign table option named mpp_execute
• misc edits (typos, corrections, wording changes)

NOT in this PR:

• "using" type info, like how to develop a greenplum FDW - this will come in a separate PR

questions:

• doe CREATE/ALTER FOREIGN TABLE support the TRIGGER and REPLICA TRIGGER clauses?
• does ALTER FOREIGN TABLE support the "ALTER [ COLUMN ] column_name SET STATISTICS ..." clause?

doc review site links:

• http://docs-lisa-fdw.cfapps.io/600/ref_guide/sql_commands/ALTER_FOREIGN_DATA_WRAPPER.html
• http://docs-lisa-fdw.cfapps.io/600/ref_guide/sql_commands/ALTER_FOREIGN_TABLE.html
• http://docs-lisa-fdw.cfapps.io/600/ref_guide/sql_commands/CREATE_FOREIGN_DATA_WRAPPER.html
• http://docs-lisa-fdw.cfapps.io/600/ref_guide/sql_commands/CREATE_FOREIGN_TABLE.html

[dyozie]

Thanks!

[adam8157]

There are two code snippets in create_foreign_table.sgml, does our doc need them?

[lisakowen]

thank you for reviewing, @adam8157 ! i was thinking that those code snippets are more developer-focused than end-user-focused, and might be better placed in the topic where we discuss how to write a foreign data wrapper. (this topic is not yet written.) do you agree?

[dyozie]

Although I'd agree that developer-focused info might be better placed elsewhere, we should weigh that against the maintainability of keeping the docs more in sync with the postgresql docs for future merges.

[lisakowen]

@dyozie - the code excerpt is not in the postgresql docs. it is a greenplum addition.