The PIN mapping of the Raspberry 2B says:
The red ones are 5V pins. Are these just used as 5V out pins when power is connected through Micro USB? Or is it also possible to power the Raspberry Pi via those pins, so that I can get rid of the Micro USB cable?
Please note: I don't want to power peripherals from these pins, I want to power the Raspberry itself, i.e. I want to get rid of the micro USB power supply.
This pin is directly connected to the 5V net, meaning indeed it is possible to power through that pin.
When under USB power, this net is supplied by USB power, but there is no reason you couldn't power it yourself, however, replicating some of the protection scheme is worthwhile to protect power supplies and prevent fires.
In my opinion, modifying the board (replacing usb header) is riskier and more error-prone than using an external supply with adequate protection.
However, the simplest solution is to make a cable from your power supply or connector of choice to micro-usb, because you may as well re-use the circuit they have there.
Taking a look at the schematics we can see the GPIO pins are attached directly to 5V net
What @Dr.Rabbit is referring to is a ressetable fuse that is used to protect from short circuit. This can be seen here as component F1. The 5V net shows ups at the right of the schematic
Note that the USB input is additionally protected from reverse power, it is a good idea to replicate both of these protection schemes in your set up.
Keep in mind that these largely protect the operator and the power supply. If the polyfuse trips due to accidental short, the board is probably dead anyway, however if you are simply running too many loads then the polyfuse will protect the on board power supply and the wall-wart from continuous over-current.
It is legitimate to use Diodes to OR power supplies and prevent reverse current. You just have to be sure to take into account the diode voltage drop or compensate for it in your schematic like what is done on the raspberry pi.
Yes, you can use the 5v pins. These pins are on a 5v rail. This will however bypass any protection circuits on the Pi. If you don't want to use the micro usb, the better thing to do is to solder your power supply to the PP1 port on the bottom of your Pi. Check the link for a complete overview of the PP connections.
https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=89522&p=628505&hilit=pp1#p628505
On a Raspberry Pi Zero W I use one of these pins to power the Raspberry. My Raspberry is a controller for an APA 102 LED strip.
The strip itself uses a lot of current, so I can't power it from the 5V pin of the Raspberry (it would most likely destroy it).
But I can easily use the 5V / 10A power supply for the LEDs to also power the Raspberry Pi through the 5V pin, hence using the pin as an input.
As mentioned in a comment, there is no reverse polarity protection, or over-voltage protection on these pins, so be careful! You could add a capacitor between the 5V and ground pin for some protection. However, a good 5V power supply should not produce a power spike when it is plugged in. So far, I did not destroy a Raspberry Pi with this setup.