Fix missing Association/AssociationSet(aka FK constraints) in the EF manifest files

This is updated PR from #100, targeting new 2.1.0 branch.

It adds missing relationships between entities, into the EntityFramework provider manifest.

New AssociationSets in ssdl (table to table?): 
- PgTables ⇔ PgTableColumns
- PgTables ⇔ PgConstraints
- PgTableColumns ⇔ PgForeignKeyColumns
- PgConstraints ⇔ PgConstraintColumns
- PgConstraints ⇔ PgForeignKeyColumns
- PgViews ⇔ PgViewColumns
- PgViews ⇔ PgViewConstraints
- PgViewColumns ⇔ PgViewForeignKeyColumns
- PgViewConstraints ⇔ PgViewConstraintColumns
- PgViewConstraints ⇔ PgViewForignKeyColumns
- PgFunctions ⇔ PgFunctionParametetrs
- PgProcedures ⇔ PgProcedureParameters

New Associations in ssdl (column to column?):
- ViewColumn → ViewForeignKeyColumn
- View → ViewConstraint
- ViewColumn → ViewForeignKeyColumn
- ViewConstraint → ViewConstraintColumn
- ViewConstraint → ViewForeignKeyColumn
- Procedure → ProcedureParameter

I have figured current status to check missing ones.
https://dl.dropboxusercontent.com/u/24560712/ef6/fixed_npgsql_msl_ssdl.png

Currently EdmGen fails to generate correct schema for target database, because associations are missing. e.g. Table has no TableColumns.