Delete lots of migrations

... in preparation for creating new initial migrations
Remove iface vrf fields; add initial migrations
Add ORM freeze thing to system migration
fridgei's DHCP things
Replace shell commands with real Python
Write all configuration to dhcpd.conf
Add dhcp_build management command; fix settings
Generated dhcpd conf name is dhcpd.conf.data
Remove unnecessary files
Add TARGET_FILE and CHECK_FILE settings
PEP8 and punctuation cleanup
Move some settings to base.py and rename them
Revert some argument and variable name changes
Fix incorrect variable names
Fix a faulty import
Remove useless code
Fix some misspelled variables in comments
PEP8 stuff
Add MacAddrField model field
StaticInterface & DynamicInterface: new mac field