Add Faculty and School to parser and model

[avihai-huji]

There are three things to discuss:

1. In the parser, should we return an error if faculty / school doesn't exist (i mean return None)?
2. Can school be null in Course model (atm they can be null)?
3. Medicine faculty has a typo in it's name, there are two separating colons instead of one, e.g. here 94124 (and also in every course that's under this faculty). should we fix it in our side?

[asaf-kali]

1. For now maybe raise an error, and see how many courses fail. For those who fail, see why: if it's a parser issue, fix it. If it is actually missing for some courses, just allow nulls.
2. Same (raise error if parsing fail, see why, decide).
3. Try to handle it in the parser