Allow code model to only update itself upon file save

After upgrading to Qt Creator 7.0, editing a source file in a largish project often stutters as it updates it's code model in real time as you type. This is very distracting and is accompanied by high CPU usage (I hear my PC fans constantly revving up and down as I type).

Please make it so the code model is only updated upon one of these configurable options:

• As you type (which seems to be the current default)
• Every N seconds
• After saving a source file (would be my preference)
• When building
• On demand (explicit user action)
• Never (code model disabled)

Currently the Code Model configuration seems to be "as you type or nothing".

While the stuttering while writing code is annoying, I still do appreciate the code model feature while perusing the code. Having the above options would give me the best of both worlds where the code model at least gives me the chance to finish a block of code and hit ctrl-S before firing all cylinders of my CPU.

Please also consider the carbon footprint of CPUs constantly updating Qt Creator code models needlessly too often.