Refactor function cobbler.utils.is_mac

Use a precompiled and faster regular expression and add more tests.
timeit with 64M iterations: 48.32 versus 42.38 seconds.
Merge pull request #412 from ciupicri/master-mac-regex

Refactor function cobbler.utils.is_mac
Speedup function cobbler.utils.is_mac

Use both lower case and upper case hexadecimal digits in the regex
instead of using the re.IGNORECASE option. Also add more tests.
timeit with 64M iterations: 42.78 versus 39.74 seconds.
Merge pull request #413 from ciupicri/master-mac-regex

Speedup function cobbler.utils.is_mac
FEATURE - adding the ability to rename interfaces on the CLI
FEATURE - adding interface rename to the web ui
Merge pull request #416 from jimi1283/issue_415

Adding interface renaming
Fixing utils, CX exceptions should be raised, not returned