scons: make sure to respect options in 'config.py' over defaults stored in opts, fix up permissions and flush the .sconsign.dblite when switching to FAST build - closes #261 and #264
scons: make sure to respect options in 'config.py' over defaults stored in opts, fix up permissions and flush the .sconsign.dblite when switching to FAST build - closes #261 and #264

git-svn-id: 06a2cde72a096d93ff72b88e3e6711b8f00772a4@1041 d397654b-2ff0-0310-9e29-ba003691a0f9

semprebon/mapnik,semprebon/mapnik,semprebon/mapnik,semprebon/mapnik,semprebon/mapnik