Improve checks for write permission of files and directories.
Don't overwrite maybe existing project files when trying to create new project and checking for project file's write permission (thanks to Yura Siamashka for reporting and his patch).


git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@2151 ea778897-0a13-0410-b9d1-a72fbfd435f5