databases/virtualpg: Update to 2.0.0

• Add pkg-plist
• Update description

Short summary of differences between earlier versions and v2:

• Now VirtualPG is available as both a standard C/C++ library (libvirtualpg) and a dynamic extension module to SQLite (mod_virtualpg).
• Now the user can freely choose his/her preferred format for DATE / TIME / TIMESTAMP values.
• Transactions (BEGIN / COMMIT / ROLLBACK) are now fully honoured also on the PostgreSQL side.
• Write operations (INSER / UPDATE / DELETE) are now allowed only if the PostgreSQL user has the corresponding GRANT permissions.
• Write operations can be enabled only for PostgreSQL Tables explicitly declaring a PRIMARY KEY.