Restructure gitignore so that binaries and build related Visual Studio files are only ignored below the src directory. This will avoid ignoring e.g. binaries in the Tools directory, which we do want to commit.

Add nunit-editor.exe previously missing due to this.
Update to Iesi.Collections 4.0.1. Include pdb to fix NH-3185.
Code cleanup
Oracle8iDialect.cs: Define atan2 and power to return double to harmonize with other dialects. Make the Linq provider also handle Math.Pow(). NH-3381.
PostgreSQLDialect.cs: Define trigonometric functions. Tests covered by Linq.MathTests. NH-3398.
Remove obsolete FirebirdDriver.cs. NH-3322.
FirebirdClientDriver.cs, FirebirdDialect.cs: Update references in code documentation.
Line endings.
Mapping/Map.cs: Give a helpful message if user doesn't specify collection-type for a sorted generic map, instead of NullReferenceException.