Added Default SystemMethods.CurrentDateTime for Oracle Backend Generator (maps to oracle keyword CURRENT_TIMESTAMP)

http://docs.oracle.com/cd/B28359_01/server.111/b28286/functions038.htm#SQLRF00629
Added SchemaName to Create, Insert and Delete Table operations for Oracle generator backend
changed oracle tests to correctly check custom schema in Create, Insert, Delete
edge case for "IsQuoted" method in Generators/Generic/GenericQuoter.cs:
method IsQuoted if parameter passed is null or empty returns false (because it is not quoted...)
Fixed Insert tests from OracleDataTests.cs
Merge pull request #478 from kidFashion/master

  Fixed Insert tests from OracleDataTests.cs
  edge case for "IsQuoted" method in Generators/Generic/GenericQuoter.cs: method IsQuoted if parameter passed is null or empty returns false (because it is not quoted...)
  changed oracle tests to correctly check custom schema in Create, Insert, Delete
  Added SchemaName to Create, Insert and Delete Table operations for Oracle generator backend
  Added Default SystemMethods.CurrentDateTime for Oracle Backend Generator (maps to oracle keyword CURRENT_TIMESTAMP)