Fix for unknown baseband on I9300

Edit 2015-03-30: I see from other sources that TWRP 2.8.6.0 could be too big for recovery partition on I9300 so beware!

After flashing the latest TWRP with Flashify, the phone fell into a boot loop. Here is a list of recovery procedures performed in case I need them again.
So, first I used a USB stick modem to get Internet. SIM extender or an original remains of the card were needed to fit the SIM card into the USB modem.

Recovery

Then, via PC, I flashed TWRP with Odin, using PDA option. This fixed the recovery and the phone booted into OS.

Baseband / Modem

However, the phone would not connect to network. The baseband was unknown and IMEI did not show up at all when trying with *#06# code on the phone.
The solution for this was to flash the modem.

1. Get the latest firmware from SamMobile
2. Extract the files to get modem.bin.
3. Download img2tar tool from xda. It is also possible to use Tar for Windows but this is safer as it generates md5 hash as well.
4. Flash the resulting modem.tar.md5 file using Odin, via Phone option (not PDA). This is with Odin 3.07.

This fixed the baseband and the phone correctly recognised that there is no SIM card.