[Calculator][Proposal]Remove partial result feature

[Riccardo Padovani]

Partial result feature is broken and there is no easy way to fix it.

E.g: 1+2x2x (result is 5) x 2. On your screen there is 5*2, but the ressul is 9.

We cannot fix it in a simple way (tbh I think we cannot have it working at all) because we have advanced functions.
If there is something different from a ^ in the calculus we can calculate wrong partial result.

E.g.
3 + (1 * 2)

This seems easy, because there is a parethesis, but if we had a * 3 we have:
displayed: 5 * 3 = 15
actual = 3 + 3 *3 = 12

Due this reason I suggest to remove the feature.

Proposed solution:
 1. Get rid of temporarly result
 2. Instead of introduce multi line formula InputField
    - When entered formula exceed InputField width, then the new line wil appear

It will be good to also do it with Formula's History, to fix issue
https://bugs.launchpad.net/ubuntu-ux/+bug/1446808
The history displays could be limited to 3 lines. After formula exceeds 3 lines, the three dots will be displayed.

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UX Comment:

We should try to proceed with the multi-line formula Inputfiled (2.) to preserve temporary results in the U.I and boost utility.

[Bartosz Kosiorek (gang65)]

We need an input from UX team. That's why I marking it as invalid for Calculator (we unable to start implementing that till we don't get ux design)