Ignore *.pyc files
New directory structure for CERIT's cmd modelers
New CERIT_SC.cmd.df derived from zenoss.cmd.df.

Features:
- df shows filesystem and error output is ignored
- type (fixedDisk, networkDisk, etc.) is detected for common filesystems
- support for zFileSystemMapIgnoreTypes
Move CERIT_SC.cmd.df -> CERIT_SC.cmd.linux.df
Run CERIT_SC.cmd.linux.df only on Linux