filed: Create all files with mode 0666

Create all files and directories by default with mode 0666 and 0777
respectively. Then rely on the appropriate umask setting in order to apply the
correct file permissions.
python: Add support for peer umask option
conf: Update default configuration with umask option
peer.c: Initilize local signal only once
archipelago: Add timeout to vlmc lock acquire

Add timeout to vlmc lock acquire. Set it by default to 15 seconds.
mapper: Restore correct map state when destroying fails
archipelago: Add umask config option

Add umask config option and make archipelago tools use it.
docs: Update upgrade-0.4 guide
conf: Add commented out 'lock_dir' option
archipelago: Catch missing tap-ctl executable