added .gitignore which makes using git-svn easier

.gitignore

@@ -0,0 +1,26 @@
+*.csproj
+*.csproj.user
+*.build
+*.mdb
+*.mdp
+*.mds
+*.dll.build
+*/*/bin
+*/*/*/bin
+*/*/*/*/bin
+*/*/*/*/*/bin
+*/*/*/*/*/*/bin
+*/*/*/*/*/*/*/bin
+bin/Debug/*.dll
+bin/*.dll.mdb
+bin/addin-db-*
+bin/*.dll
+bin/ScriptEngines/*.dll
+bin/*.maddin
+Examples/*.dll
+bin/*.exe
+OpenSim.build
+OpenSim.sln
+Prebuild/Prebuild.build
+Prebuild/Prebuild.sln
+*~